Search

Purpose: The aim of this study was to investigate the relationship between the hammering sound level and the presence of postoperative subsidence. Methods: The last five hammering sounds during the final-size broaching procedure and during the real stem insertion were recorded and analysed in 95 patients who were operated on by one of seven surgeons using two implants (Trident cup, Accolade II, Stryker; G7 cup, Taperloc Complete Microplasty Stem, Zimmer Biomet). The maximum peak was semi-automatically identified and analysed to determine the maximum C-weighted sound pressure level (LCpeak) of each of the five hammering sounds and the equivalent continuous A-weighted sound pressure (LAeq) of the entire five-sound hammering procedure. Results: Among the 95 hips, 25 (26.3%) had ≥ 3 mm of postoperative subsidence. Therefore, 125 of 475 hammering sounds (LCpeak) and 25 of 95 hammering procedures (LAeq) in both the broaching procedure and stem insertion procedure were associated with postoperative subsidence. The hammering sound level in both the broaching and stem insertion procedures were significantly weaker in patients with postoperative subsidence than in those without subsidence. Among the seven surgeons, there was intra-surgeon and inter-surgeon heterogeneity with large variance regarding the sound levels. With univariate and multivariate analyses, the hammering sound level was independently associated with postoperative subsidence in the two models. Conclusion: A weak hammering sound level was associated with postoperative subsidence in THA with a cementless stem. An objective evaluation of the hammering procedure might be useful to decrease the incidence of postoperative subsidence. [ABSTRACT FROM AUTHOR]

In the manufacturing industries, noise is one of the most common health hazards at workplaces. In wood machining, for instance, circular sawing processes in particular produce high noise emissions that often exceed the permitted limits. The main source of noise is the rotating circular saw blade, whose aeroacoustic behavior is influenced by air turbulence on the tool contour. So far, no numerical approach to study and optimize the aeroacoustic noise emissions from circular saw blades has been investigated. This paper addresses this deficit and presents a methodology for modeling the flow-induced sound generation on rotating circular saw blades based on computational fluid dynamics (CFD) simulations. With the implementation of the acoustic analogy according to Ffowcs-Williams/Hawkings, the sound pressure levels could be calculated with sufficient accuracy. With deviations between 7 and 10%, the influence of the rotational speeds could be plausibly modeled. Based on the validated numerical model, geometry variants with various modifications were investigated regarding their potential for reducing sound pressure levels. Based on a conventional reference geometry, different chip space volumes and various modifications to the tooth rim and tooth shape were investigated and evaluated as part of simulative parameter studies. Sound pressure level reductions in the range of 2.2–10.8 dB were achieved. The results obtained and the systematic approach investigated provide a suitable set of instruments for industrial practice. Digital prototypes can be designed at an early stage in the product development phase of circular saw blades regarding their aeroacoustic properties. [ABSTRACT FROM AUTHOR]

The subjective perceptions of passengers are intricately linked to the noise levels in subway stations of urban rail transit systems. In this study, comprehensive measurement was conducted on the noise environment on the platforms during operational hours at four distinct types of subway stations within an urban metro network. To ensure precise data collection, four different noise and sound pressure measurement points were strategically positioned in the middle and at both ends of each station platform. Subsequently, the platform noise data was continuously monitored throughout the operation period, yielding a time series of original data on sound pressure levels for standardized continuous measurement of the platform. The collected results spanning the entire operation period were organized into hourly sets, encompassing information on noise sources such as vehicles entering and leaving the station, the opening and closing of train doors, and platform announcements. This dataset provides original data on noise sources at subway platforms throughout the all-day train operation period, aiding researchers in understanding the sources and levels of noise at subway station platforms. Additionally, this research supports noise control on subway platforms and provides a scientific basis for predicting the acoustic environment of rail transit stations and improving the platform acoustic environment. [ABSTRACT FROM AUTHOR]

Introduction: Preserving the cochlear structures and thus hearing preservation, has become a prominent topic of discussion in cochlear implant (CI) surgery. Various approaches and soft surgical techniques have been described when approaching the inner ear. Robot-assisted cochlear implant surgery (RACIS) reaches the round window in a minimally invasive manner by following a trajectory of minimal trauma. This involves the drilling of a keyhole trajectory to the round window, through the facial recess, with no need for a complete mastoidectomy. It involves less drilling, less drilling time and less structural damage. A lot of attention has been paid to the structural traumatic causes of hearing loss but acoustic trauma during the exposure of the inner ear appears to be neglected topic. Aim: The aim was to measure the noise exposure of the inner ear during the robotic drilling of the mastoid and bony overhang of the round window. The results were compared with the milling in conventional cochlear implantation surgery. Intervention: RACIS on fresh frozen human cadavers. Outcome measurements: The equivalent frequency-weighted and time-averaged sound pressure level LAF in dB and the noise dose in % derived from a noise damage model, both obtained during RACIS. Materials and methods: The robotic drilling of 6 trajectories towards the inner ear were performed, including 4 trajectories through round window access and 2 trajectories through cochleostomy. The results were compared with the data of 7 cases of conventional CI surgery that have been described in literature. The induced equivalent sound pressure level LAF was determined via an accelleration sensor at the zygomatic arch and a calibration according to bone conduction audiometry. A noise dose for the whole procedure was calculated from the equivalent sound pressure level LAF and the exposure time using a noise damage model. A noise dose of 100% is considered a critical exposure limit and values above are considered potentially harmful, with the risk of hearing impairment. Results: The maximum LAF was 82 dB during fiducial screw placement; 87 dB during middle ear access; 95 dB for the accesses through the round window and 88 dB for the accesses through cochleostomy. The noise dose due to the HEARO®-procedure was always far below the critical value of 100%. There was no acoustic trauma of the inner ear in all cases with the noise dose being smaller than 0.1% in five out of the six cases. The maximum LAF in the seven cases of conventional CI surgery was 118 dB with a maximum cumulative noise dose of 172.6%. The critical exposure limit of 100% was exceeded in three cases of conventional CI surgery. Conclusion: RACIS provokes significantly less acoustic trauma than conventional mastoid surgery in our findings. There were no observable differences in noise exposure levels between a cochleostomy or a round window approach where the bony overhang needed to be drilled. [ABSTRACT FROM AUTHOR]

Accurately determining the initial acoustic field excitation load of a piezoelectric ultrasonic probe is essential for simulating electrical signals and calculating wall thickness during ultrasonic internal inspection of pipelines. A new method for determining the initial excitation load of the acoustic field is proposed, incorporating the focusing effect of the curved surface of pipelines on the ultrasonic signal from the piezoelectric ultrasonic probe. Finite element models were established for the new and old methods using COMSOL software, facilitating the analysis of the initial acoustic field distribution and associated electrical signal characteristics. Scenarios considered included pipelines with and without inner wall defects, and with or without a deviation angle between the pipeline and the probe. The pipeline wall thickness was calculated inversely for each condition. Comparisons with actual wall thickness revealed that the initial excitation load determined by the new method significantly improved accuracy in wall thickness inversion, compared to the published existing method. This indicates that considering the focusing effect of the curved surface of pipelines on ultrasonic signals enhances the accuracy of simulation for piezoelectric ultrasonic internal inspection. This lays the groundwork for developing a digital research and development platform tailored for the ultrasonic internal detectors of pipeline. [ABSTRACT FROM AUTHOR]

This work presents air-coupled piezoelectric micromachined ultrasonic transducers (pMUTs) with high sound pressure level (SPL) under low-driving voltages by utilizing sputtered potassium sodium niobate K0.34Na0.66NbO3 (KNN) films. A prototype single KNN pMUT has been tested to show a resonant frequency at 106.3 kHz under 4 Vp-p with outstanding characteristics: (1) a large vibration amplitude of 3.74 μm/V, and (2) a high acoustic root mean square (RMS) sound pressure level of 105.5 dB/V at 10 cm, which is 5–10 times higher than those of AlN-based pMUTs at a similar frequency. There are various potential sensing and actuating applications, such as fingerprint sensing, touch point, and gesture recognition. In this work, we present demonstrations in three fields: haptics, loudspeakers, and rangefinders. For haptics, an array of 15 × 15 KNN pMUTs is used as a non-contact actuator to provide a focal pressure of around 160.3 dB RMS SPL at a distance of 15 mm. This represents the highest output pressure achieved by an airborne pMUT for haptic sensation on human palms. When used as a loudspeaker, a single pMUT element with a resonant frequency close to the audible range at 22.8 kHz is characterized. It is shown to be able to generate a uniform acoustic output with an amplitude modulation scheme. In the rangefinder application, pulse-echo measurements using a single pMUT element demonstrate good transceiving results, capable of detecting objects up to 2.82 m away. As such, this new class of high-SPL and low-driving-voltage pMUTs could be further extended to other applications requiring high acoustic pressure and a small form factor. [ABSTRACT FROM AUTHOR]

Contactless acoustics provide a unique, flexible active means for phase-change heat transfer enhancement. However, the ultrasonic transducers used for conventional acoustic enhancement are bulky and unfavorable for integration, and the heat accumulation under high power is not conducive to long-term operation, with limited enhancement in the critical heat flux (CHF). Herein, an acoustic-enabled low-power compact heat exchanger (ALCHE) is proposed with low energy consumption and long operation duration. Based on image processing and bubble tracking algorithm, it is found that the acoustic field accelerates bubble detachment and migration for achieving superior heat flux and larger heat transfer coefficient (HTC). 1.5 kHz acoustic field performs better heat transfer performance due to its strong acoustic radiation force magnitude and excellent acoustic pressure field direction. The stronger acoustic radiation force from higher acoustic power promotes the heat transfer performance among different acoustic powers. Long-time stable operation of acoustic field enhanced heat transfer under high heat flux is achieved with low acoustic power. Our designed heat exchanger not only overcomes the limitation of traditional bulky transducers, but also provides insights into the acoustic-enabled flow boiling heat transfer process. Improving the cooling performance of high-power electronics in confined spaces remains a challenge. Herein, the authors propose an acoustic-enabled low-power compact heat exchanger that utilizes contactless acoustics as a flexible active means for enhancing phase change cooling. [ABSTRACT FROM AUTHOR]

Ultrasonic biochemical detection is important for biomarker detection, drug monitoring, and medical diagnosis, as it can predict disease progression and enable effective measures to be taken in a timely manner. However, the ultrasonic technology currently used for biochemical marker detection is directly modified on the surface of the device. The associated test methods are costly and unreliable while having poor repeatability; therefore, they cannot achieve low-cost rapid testing. In this study, a detection mechanism based on the Rayleigh scattering of acoustic waves caused by nanoparticles, which causes changes in the received sound pressure, was developed for the first time. The modification of antibodies on an insertable substrate decouples the functionalization step from the sensor surface and facilitates the application of capacitive micromachined ultrasonic transducers (CMUTs) in conjunction with Au nanoparticles (AuNPs) for CA19-9 cancer antigen detection. A corresponding detection theory was established, and the relevant parameters of the theoretical formula were verified using different nanoparticles. Using our fabricated CMUT chip with a resonant frequency of 1 MHz, the concentrations and substances of the CA19-9 antigen markers were successfully measured. In the concentration range of 0.1–1000 U/mL, the receiving voltage decreased with increasing concentration. Further investigations revealed that the influence of other interfering markers in the human body can be ignored, demonstrating the feasibility and robustness of biochemical detection based on CMUTs combined with nanoparticles. [ABSTRACT FROM AUTHOR]

Purpose: The study aims to investigate the effectiveness of DYAD606, a viscoelastic material known for its high frequency and temperature dependency, in enhancing the damping capacity of structures subjected to vibro-acoustic issues. The research question revolves around understanding how DYAD606 affects the vibration and acoustic behavior of sandwich plates, particularly focusing on its damping properties concerning frequency and temperature variations. Methods: Employing a numerical approach, the study utilizes Finite Element Method (FEM), Boundary Element Method (BEM), and Numerical Asymptotic Method (NAM) to analyze the vibration and acoustic characteristics of sandwich plates with DYAD606 cores. The formulation of the equation of motion based on Hamilton's principle and the construction of a structural modal basis facilitate comprehensive analysis. Results: The research reveals that DYAD606 effectively enhances damping across various temperature conditions. Despite a decrease in structural rigidity with rising temperatures, there is a notable improvement in acoustic damping, as evidenced by parameters such as sound transmission loss factor (STL) and sound pressure factor. Conclusion: Viscoelastic materials like DYAD606 demonstrate efficacy in attenuating vibrations and reducing noise levels in structural applications. The study underscores the importance of considering both frequency and temperature dependencies when evaluating the damping capabilities of such materials, providing insights for the development of effective damping techniques in modern systems and installations. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the complexities of two-dimensional deformations by employing the two-temperature nonlocal thermoelasticity theory. The research focuses on the coupling that occurs between mechanical waves, acoustic pressure, and the subsequent elastic material response. Understanding the ways in which the acoustic pressure influences the thermoelastic and mechanical properties of materials is the primary focus of our trip. When it comes to the modification of the thermoelastic response during the declining heat source, we explicitly investigate the impact that acoustic pressure actually plays. Method: In order to provide a narrative of the intertwined development of temperature and deformation fields in the vast canvas of two-dimensional (2D) space, theoretical formulations are constructed. Through the utilization of normal mode analysis (harmonic wave), we are able to successfully discover analytical solutions for the fundamental physical fields (wave propagation) of nonlocal physical fields. Results and Conclusion: Particular boundary conditions are incorporated into our numerical simulations in order to improve their level of precision. The numerical results are subjected to a thorough theoretical analysis, and a colorful visual depiction of the path that the investigated physical quantities followed is provided in copper material. [ABSTRACT FROM AUTHOR]

Purpose: This paper proposes a flexural ultrasonic transducer specifically designed for surface treatment of materials with delicate surfaces such as skin by acoustic cavitation at low frequencies. The goal of this preliminary study is to assess the resonance frequencies and the output sound pressure of the proposed transducer and confirm generation of acoustic cavitation on the surface of an artificial skin phantom. Methods: A transducer prototype was designed based on structural-acoustic simulation and fabricated. The proposed design employs a concave-shaped acoustic resonator with a spherical cavity, which is driven by flexural vibration of a piezoelectric ceramic disk actuator. The transducer prototype has compact dimensions of 15 mm in diameter and 8 mm in axial length, working at frequencies around flexural vibration modes of the piezoelectric disk with a thickness of 1 mm. Results: The maximum sound pressure amplitude reached 125 kPa with an input voltage amplitude of 10 V at the second resonance frequency of 167 kHz, where the third axisymmetric eigenmode was excited. Despite enhancing the maximum pressure, the sound pressure outside the resonator attenuates because the near-field distance of the irradiated sound wave is smaller than the height of the resonator. This implies that the proposed method provides the cavitation effect on material surfaces, possibly minimizing the side effect of ultrasound irradiation on the underlying structure. Cavitation generation on a urethane gel surface was directly observed by using a high-speed video camera. Conclusion: We confirmed that acoustic cavitation was generated and propelled to the target surface. It concludes that ultrasound irradiation using the proposed ultrasonic transducer could be a promising alternative for effective and safe ultrasound treatment of material surfaces. [ABSTRACT FROM AUTHOR]

Laser drilling of glass using tightly focused femtosecond laser pulses while monitoring laser-generated sound is demonstrated, aiming laser drilling controlled by laser-generated sound. The amount of laser ablation was found to have a monotonical relation to the intensity of the sound pressure. It was also found that when the laser pulses were focused on the glass surface, the sound pressure increased in the initial stage of the laser drilling and then declined as the hole became deeper. These behaviors were the result of increasing ablation caused by surface roughening and loss of sound propagation through the hole, respectively. It was further found that the movement of the objective lens (OL) toward the target material at an appropriate constant speed created a hole with a large depth and narrow entrance (a high aspect ratio); that is, the lens movement changed the performance of the laser drilling. A simple method for moving the lens using laser-generated sound was adopted in this study. The axial position of the OL was controlled by maximizing the sound pressure at each pulse irradiation to obtain a hole with a high aspect ratio, which was the same as the maximum hole depth obtained by the iterative experiments in the constant-speed control of the OL. More sophisticated control methods should be developed according to the given applications. [ABSTRACT FROM AUTHOR]

This research investigates the influence of rotation on the propagation of optical acoustic waves caused by the motion of an optical carrier in an elastic thermal environment. The study employs theoretical analysis to derive governing equations tailored to a nonlocal semiconductor medium, incorporating the interaction between acoustic waves and thermomechanics. The foundational equations of the model, influenced by photothermal and thermoelastic principles, are mathematically derived when the microstructure of the medium is taken into consideration while accounting for rotation. The model explores the medium's response to a thermal ramp originating from light-induced temperature elevation. The mathematical model is solvable in two-dimensional (2D) using the normal mode method, and numerical solutions offer insights into various physical fields, such as displacements, temperature, acoustic pressure, mechanical distributions, and carrier density diffusion. Employing the harmonic wave method, some graphical representations of the rotation parameter are obtained, both with and without the influence of the nonlocal parameter. Theoretical analysis includes a comprehensive examination, comparison, and discussion of the effects of these parameters on the system subjected to ramp-type heating. [ABSTRACT FROM AUTHOR]

Dry turning reduces the environmental impact and costs associated with cutting fluids, but it challenges the optimization of tool life due to the generated heat. This study evaluated machine learning models to predict tool life (T) during the dry turning of AISI H13 steel by analyzing cutting speed (Vc), feed rate (f), and depth of cut (ap). Nineteen experiments were conducted using a central composite design (CCD), evaluating machining cost, tool life, sound pressure level (SPL), chip removal rate, and machining force. Statistical analysis included calculations of central tendency, dispersion, and Pearson correlation. Five machine learning models were compared: linear regression, decision tree regression, random forest regression, multi-layer perceptron (MLP) regression, and stochastic gradient descent (SGD) regression. The evaluation metrics were MSE, RMSE, and R 2 . The random forest and stochastic gradient descent models proved to be promising. The random forest model stood out with high R 2 values, indicating greater precision. Linear regression and stochastic gradient descent also performed well in predicting sound pressure levels. The consistency of the random forest model in both training/testing and prediction phases highlights its robustness and adaptability to different tools and machining setups. In contrast, the multi-layer perceptron model exhibited greater variability, reflecting its sensitivity to hyperparameter settings. The results demonstrate the effectiveness of the random forest model in predicting tool life, contributing to reduced operational costs and increased manufacturing efficiency. [ABSTRACT FROM AUTHOR]

Purpose: A theoretical framework based on coherent reflection and filter theory predicts that the phase-gradient delays of stimulus frequency otoacoustic emissions (SFOAEs) are correlated with tuning sharpness in the mammalian cochlea. In this paper, we use a computational model of the cochlea to test this theory and to evaluate how SFOAE phase-gradient delays may be used to estimate the sharpness of cochlear tuning. Methods: This study is based on a physiologically motivated model which has been previously shown to predict key aspects of cochlear micromechanics. Cochlear roughness is introduced to model the reflection mechanism which underlies SFOAE generation. We then examine how varying the values of key model parameters or of the sound pressure level of the stimulus affects the relation between cochlear tuning and SFOAE delays. Finally, we quantify the ability of model simulations of SFOAE phase-gradient delays to provide reliable estimates of the tuning sharpness of the model. Results: We find that variations of model parameters that cause significant broadening of basilar membrane (BM) tuning typically give rise to a sizeable reduction in SFOAE phase-gradient delays. However, some changes in model parameters may cause a significant broadening of BM tuning with only a moderate decrease in SFOAE delays. SFOAE delays can be used to estimate the tuning sharpness of the model with reasonable accuracy only in cases where broadening of cochlear tuning is associated with a significant reduction in SFOAE delays. Conclusion: The numerical results provide key insights about the correlations between cochlear tuning and SFOAE delays. [ABSTRACT FROM AUTHOR]

This study investigates the impact of the noise radiated from airplanes, urban rail transit, high-speed railways, and urban roads on residents near an airport. The results showed that all respondents near the airport were highly annoyed with airplane noise, and some remain annoyed with the noise from the urban rail transit and high-speed railway connecting to the airport. The most detrimental aspect of transportation noise was sleeping disturbance. Transportation noise from 19:00 to 24:00 primarily caused the annoyance of surrounding residents. Airplane noise is the largest source of sound pollution in residences in the region adjacent to the elevated urban rail transit and airport. The insertion loss of vertical sound barrier with a height of 2.4 m at the points 25 m away from the track centerline is 6.9–8.6 dB, but the sound pressure level below 40 Hz is amplified owing to the structure-borne noise radiating from the barrier itself. The presence of sound barriers can reduce the high annoyance level from 24 to 8.2%. [ABSTRACT FROM AUTHOR]

Background: Today, magnetic resonance imaging (MRI) is rarely used in managing the care of premature neonates. This is in large part due to the medical and logistical challenges associated with moving neonates from the neonatal intensive care unit (NICU) to the radiology department. Furthermore, acoustic noise associated with MR scanning poses safety concerns for both practitioners and neonatal patients. A small-format 3.0-T neonatal scanner was recently developed and placed within the NICU to address these logistical and acoustic challenges. Objective: To compare acoustic noise measurements of a small-format 3.0-T neonatal MRI scanner with conventional adult-sized 1.5-T and 3.0-T MRI scanners using identical neonatal head imaging protocols. Materials and methods: Sound pressure level (SPL) measurements of a standard imaging protocol were made in a small-format neonatal 3.0-T MRI scanner as well as in adult-sized 1.5-T and 3.0-T scanners. SPL measurements were made with a Brüel & Kjær sound level meter model 2250. The statistical significance of the differences in SPL between scanners was determined using one-way ANOVA. Results: Average sound pressure level values were measured in unweighted decibels (dB) and A-weighted decibels (dBA) for all imaging sequences in the protocol. The average A-weighted SPLs for the NICU from 1.5-T and 3.0-T MRI scanners were 81.02 ± 0.28 dBA, 87.00 ± 0.85 dBA, and 94.91 ± 0.65 dBA, respectively. SPLs at the isocenter of the NICU MRI scanner were 5.98 dBA quieter than in the 1.5-T scanner (P=0.007), and 13.89 dBA quieter than in the 3.0-T scanner (P<0.001). For staff standing next to the scanner, the NICU scanner was 20.24 dBA quieter than the 1.5-T scanner (P<0.001) and 19.28 dBA quieter than the 3.0-T scanner (P<0.001). Conclusion: The NICU 3.0-T MRI system is significantly quieter than conventional adult-sized MRI systems, improving safety for neonatal patients. Significant reductions in SPL were also noted inside the screen room where clinicians may be present during scanning. [ABSTRACT FROM AUTHOR]

The study determined the impact of restrictions introduced by the Ministry of Health in connection with the COVID-19 pandemic on traffic and sound pressure levels in the university building and its immediate vicinity. Mickiewicza Street was selected for the study. It is one of the city's busiest streets, located relatively close to the old historic center, and is the main artery connecting the north and south of the city. There are residential buildings on this street, but primarily offices and institutions, as well as schools and universities. Noise near the street and in buildings located relatively close to the road can be a serious problem in places where peace is required (e.g., libraries, reading rooms, university halls). Therefore, the acoustic comfort needed in these places may be disturbed, and the perception of knowledge acquisition may be limited. The aim of the work was achieved through measurements and analysis of street traffic intensity and sound pressure levels, taking into account pandemic restrictions. Then, statistical analyses were performed, which showed significant variability in traffic intensity and sound pressure values in individual periods of the pandemic. The pandemic's beginning was mainly characterized by a significant decrease in the above data, deviating from the norm. In the pre-pandemic period, an average of 47,733 vehicles passed through the street daily, and the median sound pressure was Leq.OUT = 62.0 dBA outside the building and Leq.INS = 44.0 dBA inside. During the greatest restrictions, a period called "lockdown," the number of cars driving decreased a little to an average of 44,153 per day, but there were days with 10,000–20,000 cars passing. In turn, noise decreased to 59.9 dBA for Leq.OUT and 43.2 dBA for Leq.INS. Between the first and second waves of infections, traffic was comparable to the post-pandemic period (an average of 69,027 cars per day), and noise also increased to Leq.OUT = 64–65 dBA and close to Leq.INS = 47.5 dBA. Studies have shown that noise on Mickiewicza Street is mainly caused by traffic (correlation coefficient: r = 0.92 for Leq.OUT and r = 0.86 for Leq.INS). The sound pressure level is high outside (Leq.OUT = 63.9 dBA) but relatively low inside the building (Leq.INS = 47.0 dBA) and should not negatively affect university staff and students (Leq.WH < LWH.acc). Based on the analyses, three stages show society's approach to the COVID-19 pandemic: (1) fear of the COVID-19 pandemic; (2) relaxation after restrictions; (3) getting used to the COVID-19 pandemic. These periods did not correlate with the development of the pandemic or the number of people infected and dead. [ABSTRACT FROM AUTHOR]

Non-invasive diagnostic modalities are integral to cardiovascular care; however, current systems primarily measure peripheral pressure, limiting the breadth of cardiovascular prognostication. We report a novel approach for extracting left side heart sounds using a brachial cuff device. The technique leverages brachial cuff device enhanced signal resolution to capture pressure fluctuations generated by cardiohemic system vibrations, the sound pressure waveform. We analyze left heart catheterization data alongside simultaneous brachial cuff device measurements to correlate sound pressure waveform features with left ventricle (LV) contractility. The extracted sound pressure waveform reveals two prominent oscillatory wave packets, termed WP1 and WP2, originating from cardiac structure vibrations associated with LV contractions and relaxation. We demonstrate that WP1 originates from LV contraction during systolic blood ejection through the aortic valve (AV) and is correlated with LV isovolumetric contraction, clinically measured by LV dPdt-max (Pearson-R = 0.65, p < 0.001). Additionally, we show that WP2 comes from LV elongation required for blood flow deceleration at the end of systole, causing AV closure, and is correlated with LV isovolumetric relaxation, measured by LV ndPdt-max (Pearson-R = 0.55, p < 0.001). These findings highlight the value of cuff sound pressure waveforms in providing insights about dynamic coupling of the LV-Aorta complex for non-invasive assessment of LV contractility. [ABSTRACT FROM AUTHOR]

Flow-induced noise during the charging of hydrogen fuel for a fuel cell electric vehicle is numerically analyzed. The noise over the entire storage system is predicted by solving the unsteady version of the Reynolds-averaged Navier–Stokes equations and the Ffowcs Williams–Hawkings acoustic analogy. The accuracy of the simulation results is validated by comparing pressure, temperature, and sound pressure levels with experimental data. The contribution of each component to total noise is investigated by separately setting the integration surfaces of the acoustic analysis, and it is found that the receptacle produces the largest noise level. The large acoustic source terms, calculated by the total derivative of the pressure, occur where the pipe bends and at narrow passages of check valves. From the comparative analysis of different manifold branching configurations, a layout in which all the pipe junctions are concentrated in a single manifold leads to increased noise levels. [ABSTRACT FROM AUTHOR]

Abstract—The article presents the results of an experiment on assessing subjective indicators of acoustic perceptibility by pedestrians (experts) of a vehicle approaching at a constant speed and some conclusions. Subjective indicators of perceptibility were defined as the distance between the vehicle and the expert, at the moment when the expert heard (recorded) the sound of an approaching car, as well as the time of the car's approach to the expert at that moment. Subjective indicators of perceptibility are compared with the objective parameters of car noise measured in accordance with UN Regulation no. 138: the sound pressure level, its frequency response, and the sound level. The study is motivated by the problem of traffic safety of electrified vehicles with low noise, which include, in particular, electric cars and electric scooters. The article publishes the first results of a research paper devoted to increasing the perceptibility of low-noise vehicles for pedestrians without damaging the acoustic ecology of cities and suburbs. [ABSTRACT FROM AUTHOR]

An immersion based Capacitive Micromachined Ultrasonic Transducer (CMUT) is modelled and investigated. Analysis on the displacement and output pressure is done using Finite Element Method (FEM) for different parameters of membrane thickness, gap thickness, width of the membrane, liquid material and bias voltage applied. With effectively optimizing the device parameters and the bias a satisfactory pulse shape has been achieved. From our observation it can be seen, bias potential applied must be kept high in order to get a better displacement on the membrane that will result in more output pressure in water immersion medium than air as the coupling medium. The coupling medium has profound effect on the propagation of acoustic pressure as is evident for different immersion environment analysed. [ABSTRACT FROM AUTHOR]

Purpose: The Cold-Rolled Carbon (CRC) steel is a widely used material for automobile, aerospace and machinery applications where the radius of curvature plays a vital role in their vibrational characteristics. Therefore, by identifying the factors that influence structural integrity and acoustic emissions, engineers can tailor designs to enhance performance and efficiency of those structures. Methods: Hence, this study investigates the relationship between boundary conditions and the radius of curvature in shaping the vibro-acoustic behavior of CRC shell structures. The 3D solid structures at different radius of curvatures R=1000mm, 1500mm, and 2000mm were created, then imported into ANSYS workbench to perform modal, harmonic response and harmonic acoustics analysis. Results: As a result, minimum sound power level (SWL) was noticed from shell structures with a smaller radius of curvature (R=1000mm) while the excitation frequency was less than 500Hz. However, at higher frequency ranges (from 500Hz to 2000Hz), the shells with 1500mm and 2000mm curvature radius performed better in terms of SWL. Specifically, one side fixed 2000mm radius CRC shell structure produced the lowest far-field mic noise of 73.219dB, which is 7.5% less than the noise recorded at all side fixed condition for the same structure. Conclusion: Hence, this study recommends smaller curvature radius (R=1000mm) for shell structures working under excitation frequency less than 500Hz for an effective vibration and noise control. Otherwise, higher curvature radius (i.e) above 2000mm is recommended if the excitation frequency range exceeds 500Hz. [ABSTRACT FROM AUTHOR]

Restoration of vulnerable marine habitats is becoming increasingly popular to cope with widespread habitat loss and the resulting decline in biodiversity and ecosystem services. Lately, restoration strategies have been employed to enhance the recovery of degraded meadows of the Mediterranean endemic seagrass Posidonia oceanica. Typically, habitat restoration success is evaluated by the persistence of foundation species after transplantation (e.g., plant survival and growth) on the short and long-term, although successful plant responses do not necessarily reflect the recovery of ecosystem biodiversity and functions. Recently, soundscape (the spatial, temporal and frequency attribute of ambient sound and types of sound sources characterizing it) has been related to different habitat conditions and community structures. Thus, a successful restoration action should lead to acoustic restoration and soundscape ecology could represent an important component of restoration monitoring, leading to assess successful habitat and community restoration. Here, we evaluated acoustic community and metrics in a P. oceanica restored meadow and tested whether the plant transplant effectiveness after one year was accompanied by a restored soundscape. With this goal, acoustic recordings from degraded, transplanted and reference meadows were collected in Sardinia (Italy) using passive acoustic monitoring devices. Soundscape at each meadow type was examined using both spectral analysis and classification of fish calls based on a catalogue of fish sounds from the Mediterranean Sea. Seven different fish sounds were recorded: most of them were present in the reference and transplanted meadows and were associated to Sciaena umbra and Scorpaena spp. Sound Pressure Level (SPL, in dB re: 1 μPa-rms) and Acoustic Complexity Index (ACI) were influenced by the meadow type. Particularly higher values were associated to the transplanted meadow. SPL and ACI calculated in the 200–2000 Hz frequency band were also related to high abundance of fish sounds (chorus). These results showed that meadow restoration may lead to the recovery of soundscape and the associated community, suggesting that short term acoustic monitoring can provide complementary information to evaluate seagrass restoration success. [ABSTRACT FROM AUTHOR]

Plasma spray is a promising technology for surface protection and modification in many industrial application fields. However, the low adhesive or cohesive strength of the plasma sprayed coatings limited their further application. The cohesive strength was enhanced 115% ultra-sonicating the substrate during the plasma spraying process of Ni-10wt.%Al coatings. With the increase of power density from 0 to 1.32 W/cm2, the porosity, residual stress and strain were all decreased. However, when the power was further increased to 2.20 W/cm2, the porosity, residual stress and strain were all increased. Ultrasonic energy and the ultrasonic effects of acoustic pressure, acoustic streaming, heat effect, and cavitation effect would affect the physical processes of wetting, filling and solidification of the molten droplets during the plasma spraying process, affecting the microstructure and cohesive strength of the plasma sprayed coatings. The ultrasonic energy and ultrasonic effects which are affected by the ultrasonic power density affecting the fundamental physical processes is the key to enhance the cohesive strength of the plasma sprayed coatings. [ABSTRACT FROM AUTHOR]

The flow recirculation effect on the noise measurement of a multi-rotor unmanned aircraft system (UAS) hovering in a closed anechoic chamber is experimentally characterized in this work. The measured acoustic spectrogram reveals that the recirculation forms around 30 s after the UAS's take-off, manifested as prominent fluctuations in blade passage frequency and its harmonics. However, the instantaneous overall sound pressure level shows no obvious increase with the development of the recirculation. The result indicates that the recirculation effect does not significantly change the total acoustic energy but increases the uncertainties in the spectral distribution, which can be quantified by spectral entropy. The quantitative analysis of different noise components shows that the recirculation has a minimal effect on the tonal noise levels but slightly increases the broadband noise level out of the rotors' plane. The results from parametric tests suggest that this broadband noise increment has a positive correlation with the UAS's hover height but a negative correlation with the UAS's gross mass. The comparison with existing studies highlights the difference in the recirculation effect on the noise of isolated rotor(s) and free-flying multi-rotor UAS in confined spaces. [ABSTRACT FROM AUTHOR]

Purpose: Patients suffering from Ménière's disease (MD) experience vertigo, and impairments in hearing and quality of life (QoL). This study aims to investigate the impact of cochlear implantation (CI) on various aspects affecting patients with MD. Methods: A single tertiary centre's CI database for CI recipients with MD between 2014 and 2022 was screened retrospectively. Hearing, vertigo, tinnitus symptoms, and hearing-related QoL were assessed. Pre- and postoperative hearing tests in conjunction with subjective outcome measures by visual analogue scale (VAS) and validated tools such as the Dizziness Handicap Inventory (DHI), Tinnitus Handicap Inventory (THI) and Nijmegen Cochlear Implant Questionnaire (NCIQ), as well as the assessment of the pre- and postoperative Functional Level Scale (FLS) were examined. Results: Eleven ears were included (median age: 59 years at implantation). Following implantation, there was a significant enhancement in Word Recognition Scores at sound levels of 65 dB and 80 dB compared to before treatment (preop vs. 12 months postop: p = 0.012). However, no significant enhancement was observed for 50 dB. MD-related impairments improved significantly postoperatively, as measured by the VAS (vertigo: p = 0.017; tinnitus: p = 0.042), DHI (p = 0.043), THI (p = 0.043) and NCIQ (p < 0.001). The FLS improved significantly (p = 0.020). Conclusion: CI has positive effects on all areas examined in our cohort. However, discrimination of speech at low sound pressure levels remained problematic postoperatively. In patients suffering from MD, the prioritized treatment goals include not only improved hearing but also the rehabilitation of vertigo and tinnitus, as well as the enhancement of QoL. Validated instruments are useful screening tools. [ABSTRACT FROM AUTHOR]

This study explored subjective responses towards various environmental quality parameters. It would be helpful to approach an overall comfort improvement relating to physics. In order to investigate the combined effects of sound, light and heat on the overall comfort of pedestrians, which could be evaluated by overall comfort vote, two residential areas in Yubei District, Chongqing (a Cfa city in China) were selected for field measurements and questionnaires. Three were three key findings were concluded based on subjective responses to environmental parameters via multiple linear regression. First, the average outdoor neutral temperature, mean neutral sound level and neutral illumination intensity were determined to be 26.6 °C (determined by physiologically equivalent temperature), 56.5 dBA (determined by A-weighted equivalent continuous sound level) and 21.4 klx (determined by LUX), respectively. Second, considering the effects of both physiology and psychology, thermal perceptions varied for acoustic and light environments. Residents partially had lower neutral temperatures at the noisy condition. Third, environmental quality factors had a significant effect on overall comfort. Positive correlation between physiologically equivalent temperature and overall comfort vote was found (sig < 0.000); while the effects of sound pressure and light intensity were not always significant. Hence, thermal stress played a significant role in people's overall comfort. This study has explored the effects of three environment quality parameters on human perceptions. It provided better understanding against dwellers' feelings under complex circumstances. Future urban design and planning works should consider the cooling factors regarding contextual acoustical and visual environments. [ABSTRACT FROM AUTHOR]

To address the serious acoustic performance deterioration induced by air leakage in the low-frequency range and the asynchronous vibration in electroacoustic transduction structures near the resonant frequency, a novel sealing strategy is proposed that targets one of the most widely reported piezoelectric MEMS speaker designs. This design consists of multiple cantilever beams, in which the air gaps between cantilevers are automatically and selectively filled with liquid polydimethylsiloxane (PDMS) via the capillary effect, followed by curing. In the proof-of-concept demonstration, the sound pressure level (SPL) within the frequency range lower than 100 Hz markedly increased after sealing in an experiment using an IEC ear simulator. Specifically, the SPL is increased by 4.9 dB at 20 Hz for a 40 Vpp driving voltage. Moreover, the deteriorated SPL response near the resonant frequencies of the cantilever beams (18 kHz–19 kHz) caused by their asynchronous vibration induced by the fabrication process nonuniformity also significantly improved, which successfully increased the SPL to approximately 17.5 dB. Moreover, sealed devices feature nearly the same SPL response as the initial counterpart in the frequency band from 100 Hz to 16 kHz and a total harmonic distortion (THD) of 0.728% at 1 kHz for a 40 Vpp driving voltage. Compared with existing sealing methods, the current approach offers easy operation, low damage risk, excellent repeatability/reliability and excellent robustness advantages and provides a promising technical solution for MEMS acoustic devices. [ABSTRACT FROM AUTHOR]

The accuracy of ultrasonic nondestructive examination is limited by the limitation of near field diffraction. With the development of nearfield optical, angular spectrum method is introduced into the acoustic field, which provides a significant direction for the ultrasonic diffraction limit resolution detection. The main research of this paper is the transmission of near field ultrasound in thin workpiece and the law of the interaction of tiny flaws. The paper establishes the relationship between the longitudinal wave signal and the structure of the workpiece and the types of flaws. A method is found that whether there are flaws can be determined near field area by analysing the acoustic field characteristics of workpiece surface. Finally, comparing the calculation results with the finite element simulation, they verify each other, the method turns out to be correct in this paper. The model can also be used to improve the ultrasonic noise reduction algorithm and the extraction of minimal defect feature. It has a greatly practical significance. [ABSTRACT FROM AUTHOR]

The parameters of the ultrasonic phased array transducer are composed of frequency, array element width, array element spacing, and number of array elements, and their reasonableness is crucial for improving the detection performance of small defects, by optimizing its key parameters to complete the precise regulation to achieve more efficient acoustic field focusing and steering ability, thus optimizing the application of industrial nondestructive testing (NDT). The study firstly derives a mathematical model of focusing and steering of multi-element sound field based on the unit far-field sound pressure equation; numerically analyzes the effects of different elemental parameters on the focusing and steering performance of the PAUT by using MATLAB software; and simulates the optimized parameter conditions by combining with the COMSOL Multiphysics software, to demonstrate the improvement effect on the detection performance of small defects; finally, the optimized parameters are verified by experimental methods. The practical effect of the parameter optimization is verified by experimental methods, and the experimental results confirm the theoretical predictions, show substantial improvement in defect detection, and further strengthen the application value of the theoretical model. In this study, a parameter optimization method based on the combination of theory and multiple simulation software is proposed for the first time, which clearly elaborates the challenges of small defect detection by optimizing the transducer parameters in practical engineering applications, and deepens the theoretical basis of phased array ultrasound (PAUT) technology in industrial inspection, emphasizes the key role of parameter optimization in PAUT applications, and provides a strong theoretical and experimental support. [ABSTRACT FROM AUTHOR]

In this paper, we apply a framework based on decomposition techniques to study the synchronization of flow velocity with acoustic pressure and heat release rate in swirl flames. The framework uses the extended proper orthogonal decomposition to identify regions of the velocity field where velocity and heat release fluctuations are highly correlated. We apply this framework to study coupled interactions associated with period-1 and period-2 type thermoacoustic instability in a technically premixed, swirl-stabilized gas turbine-type model combustor operated with hydrogen-enriched natural gas. We find the structures in the flame surface and the heat release rate correlated with the dominant coherent structures of the flow field using extended POD. We observe that the correlated structures in the flow velocity, flame surface and heat release rate fields share the same spatial regions during thermoacoustic instability with period-1 oscillations. In the case of period-2 oscillations, the structures from flame surface and heat release rate field are strongly correlated. However, these structures contribute less to the coherent structures of the flow field. Using the temporal coefficients of the dominant POD modes of the flow velocity field, we also observed 1:1 and 2:1 frequency locking behaviour among the time series of acoustic pressure, heat release rate and the temporal coefficients of the first two dominating POD modes of velocity field during the state of period-1 and period-2 oscillations, respectively. These frequency-locked states, which indicate the underlying phase-synchronization states, correlate with coherent structures in the flow velocity field. [ABSTRACT FROM AUTHOR]

The acoustic and electrical properties of a 128-element ultrasonic transducer designed to generate high-intensity focused ultrasound in air in the low-frequency ultrasonic range are investigated. To reduce parasitic grating maxima of the acoustic field, a spiral arrangement of piezoelectric elements on a spherical base was used. The operating frequency of the transducer was 35.5 kHz, and the diameter of the source and focal length were approximately 50 cm, significantly exceeding the wavelength (approximately 1 cm). This selection of parameters allowed for effective focusing, with localization of wave energy in a small focal region, thereby achieving extremely high levels of ultrasonic intensity. The parameters of the ultrasonic field were studied using a combined approach that included microphone recording of the acoustic pressure and measuring the acoustic radiation force acting on a conical reflector. Acoustic source parameters were determined from the two-dimensional spatial distribution of the acoustic pressure waveform, which was measured by scanning the microphone in a transverse plane in front of the source. Numerical modeling of nonlinear wave propagation was also used based on the Westervelt equation to simulate the behavior of intense waves. The acoustic pressure level reached 173 dB, with a focal spot size comparable to the wavelength. [ABSTRACT FROM AUTHOR]

A modification of Dean's method is proposed for determining the impedance in the case of a nonuniform sound field on the front and bottom surfaces of a resonator. Instead of acoustic pressures in Dean's formula, the modification uses the coefficients of eigenfunctions, which correspond to a uniform acoustic pressure distribution on the front and bottom surfaces of the resonator. The eigenproblem is solved by the finite element method; the coefficients of the eigenfunctions are found by the least squares method. At the current stage of research, the full-scale experiment has been replaced by numerical simulation in a linear formulation of sound propagation in an impedance tube with normal wave incidence with a honeycomb resonator attached to it. The inhomogeneity of the pressure field over the cross section of the resonator is created from the different positions of holes in the resonator face plate. The study is done for a different number of acoustic pressure measurement points at the bottom of the resonator. Calculations show that the proposed method is efficient and provides good agreement with the straight method for determining impedance. However, the possibilities of using modification of Dean's method in full-scale measurements are limited, because accurate resonator impedance determination requires a large number of measurement points. [ABSTRACT FROM AUTHOR]

A method is proposed for quickly estimating the sonic boom characteristics from supersonic passenger aircraft under standard atmospheric conditions. The piecewise linear temperature profile and absence of atmospheric wind make it possible to completely reduce the problem of the geometry of sonic boom wave propagation to an algebraic form. For acoustic pressure, an analytical solution is formulated using the nonlinear geometrical acoustics approach. The dependence of the geometry of sonic boom wave propagation on the cruising flight parameters of a supersonic passenger aircraft is analyzed. Under the conditions of SBPW (Sonic Boom Prediction Workshop) 2020, the overpressure signatures on the ground from the X-59 demonstrator were calculated. [ABSTRACT FROM AUTHOR]

Purpose: Tone-pip-evoked otoacoustic emissions (PEOAEs) are transient-evoked otoacoustic emissions (OAEs) that are hypothesized to originate from reflection of energy near the best-frequency (BF) cochlear place of the stimulus frequency. However, individual PEOAEs have energy with a wide range of delays. We sought to determine whether some PEOAE energy is consistent with having been generated far from BF. Methods: PEOAEs from 35 and 47 dB SPL tone pips were obtained by removing pip-stimulus energy by subtracting the ear-canal sound pressure from scaled-down 59 dB SPL tone pips (which evoke relatively small OAEs). PEOAE delays were measured at each peak in the PEOAE absolute-value waveforms. While measuring PEOAEs and auditory-nerve compound action potentials (CAPs), amplification was blocked sequentially from apex to base by cochlear salicylate perfusion. The perfusion time when a CAP was reduced identified when the perfusion reached the tone-pip BF place. The perfusion times when each PEOAE peak was reduced identified where along the cochlea it received cochlear amplification. PEOAEs and CAPs were measured simultaneously using one pip frequency in each ear (1.4 to 4 kHz across 16 ears). Results: Most PEOAE peaks received amplification primarily between the BF place and 1–2 octaves basal of the BF place. PEOAE peaks with short delays received amplification basal of BF place. PEOAE peaks with longer delays sometimes received amplification apical of BF place, consistent with previous stimulus-frequency-OAE results. Conclusion: PEOAEs provide information about cochlear amplification primarily within ~ 1.5 octave of the tone-pip BF place, not about regions > 3 octaves basal of BF. [ABSTRACT FROM AUTHOR]

The article is devoted to the study of the process of removing moisture from capillary-porous materials by its dispersion during the collapse of cylindrically-shaped cavitation bubbles formed in the capillaries of the material under ultrasonic exposure. A model has been proposed and developed that made it possible to explain the mechanism of dispersion during realization of the life cycle of a bubble in a capillary — slow growth, rapid expansion with deformation, and subsequent collapse. The range of sound pressure levels at which dispersion begins (from 150 dB) to the level at which bubbles reach the size of the capillary and the increase in the drying efficiency stops (170 dB) has been determined theoretically. It was also shown that for maximum efficiency in moisture removal, the size of the dehydrated sample must correspond to the ultrasonic wavelength in air. The mechanism of ultrasonic dispersion of liquid during drying has been confirmed experimentally and it has been established that to reduce the drying time by more than 40%, exposure with a level in the range of 165–170 dB is necessary, and the dried materials must be placed in the form of particles or layers having dimensions or thicknesses corresponding to the ultrasonic wave length. The practical implementation of ultrasonic drying using the example of food products (red beets) confirmed the effectiveness of the proposed mechanism and ensured a reduction in drying time by 1.9 times on reducing energy demand by 1.6 times. [ABSTRACT FROM AUTHOR]

The effect of high-intensity ultrasonic treatment (which can generate cavitation) on the microstructure of aluminum (Al) ingots has been widely studied. In this work, a stainless steel thin-walled sleeve was placed in a crucible to separate the 2219 Al melt into two parts: inside and outside the sleeve. By applying the ultrasound in the melt inside the sleeve, a low-intensity ultrasonic field (where the acoustic pressure is lower than the cavitation threshold) was introduced into the melt outside the sleeve. The influence of low-intensity ultrasound on the temperature gradient of the pasty melt as well as the refinement efficiency was explored. The result shows that low-intensity ultrasonic can induce high-frequency forced vibration to the grains and reduce the solid–liquid interfacial thermal resistance. In addition, by comparing the microstructure inside and outside the sleeve, it was found that there was no significant difference in the size and morphology of the grains and eutectic phase. This indicates that the cavitation effect is not necessary for grain refinement, and low-intensity ultrasonic can also produce a significant microstructure improvement on Al alloys. [ABSTRACT FROM AUTHOR]

The acoustic field calculation model of ultrasonic vibration-mixed cement slurry is established to investigate the preparation and optimization process of the slurry as well as to study the dispersion mechanism of cement particles under the action of ultrasound. The acoustic field distribution of freshly mixed cement slurry in various mixer structures at 20 kHz is calculated by using Finite Element Method (FEM) in conjunction with multi-physical field simulation. The sound field is radially spread and produces a standing wave field with sound pressure amplitude amplified close to the wall. Average sound pressure and ultrasonic effect distance at the mid-axis likewise increase as the outer diameter of the mixer bottom plate increases, and so are the positive and negative sound pressure limits in the cement slurry. The movement of cavitation bubbles can be intensified by ultrasound with a larger acoustic pressure amplitude, hence promoting the ultrasonic cavitation effect. This can be accomplished by solving the Rayleigh–Plesset equation to determine the change rule of cavitation bubbles under the effect of different acoustic pressures. The results show that the narrow space adjacent to the wall and the bottom center of the mixer arch region are the locations of the cavitation effect's core zone when the cavitation numerical simulation is utilized in conjunction with the acoustic field calculation, and the center section is lower in vertical height than the core zone along the wall. Lastly, the simulation results were verified using laser vibrometer combined with acoustic-structural coupling relations. [ABSTRACT FROM AUTHOR]

In order to investigate the acoustic oscillation characteristics of gas–liquid pintle rocket engines and elucidate the path by which spray combustion process provides energy to the combustor pressure oscillation, a LOX/GCH4 pintle engine with rectangular combustor was designed. By adding transverse velocity disturbance for the first time, the acoustic response of spray combustion process was simulated, and the effect of excitation amplitude on acoustic response was researched. Numerical results show that the adopted transverse velocity disturbance can excite the first-order transverse acoustic oscillation with same excitation frequency in the engine combustor. The acoustic response maintenance mechanism under extrinsic excitation is summarized for pintle engines. Besides, the temperature distribution inside the engine combustor tends to be uniform, and the low-frequency oscillation caused by the flame transverse swing gradually disappears. The amplitude of combustor pressure oscillation is dominated by excitement amplitude and phase difference between the pressure and heat release in combustion reaction region. In addition, the time-averaged combustor pressure can be amplified mainly by transverse velocity disturbance. The research work can provide a reference for related fire tests on the acoustic response of a subscale gas–liquid pintle engine. [ABSTRACT FROM AUTHOR]

The impact-echo method (IE) is a non-destructive testing method commonly used in civil engineering. We propose a completely new approach for air-coupled actuation based on supersonic jet flow. The impinging jet sound generates continuously high sound pressures with a broad frequency bandwidth. This novel concept of utilising aeroacoustic sound for air-coupled IE was evaluated on two concrete specimens and validated using a classical IE device with physical contact. The results show a high agreement with the expected frequencies. Delaminations are correctly detected in depth and size. This proves the high reliability of air-coupled IE based on supersonic jet flow. [ABSTRACT FROM AUTHOR]

A computational and theoretical study of the properties of the well-known Chuprov waveguide invariant (CI) was carried out in a plane-parallel Pekeris waveguide. In contrast to earlier works, in which predominantly omnidirectional (monopole) sources were used as a source and sound pressure fields (scalar fields) were studied, in this work not only scalar, but also vector fields formed in the waveguide by directional-combined multipole sources with directivity in both horizontal and vertical planes are investigated. A differential equation has been obtained that makes it possible to fairly accurately calculate the CI values under different conditions of signal propagation and different depths of the sources and receivers. This makes it possible, in a simpler way than "total computer simulation," to predict the invariance (stability) of the CI when both the hydrophysical conditions in the waveguide and the geometry of the experiment are varied. It is shown that the directivity of sources in the horizontal plane has virtually no effect on the properties of the CI, and the directivity in the vertical plane leads to a shift in the fan structure of the signal amplitude fields, but has little effect on the CI values. The properties of the fan structure change similarly when using vertical projections of the vibrational velocity vector: despite the fact that another analytical relation different from scalar fields is used to calculate the CI, the CI value is close to (1) at all frequencies and distances, except for those at which new modes or dislocations appear. At these frequencies and in these zones, alternating emissions with different signs and magnitudes occur. It is concluded that the stability of the CI allows the application of signal processing algorithms developed for scalar fields and nondirectional sources to vector–scalar fields generated, including with the use of directional sources. [ABSTRACT FROM AUTHOR]

Under the influence of aging aggravation, more and more the elderly people spend most of their time in medical buildings. However, there is still a lack of research on the elderly satisfaction with the physical environment in medical buildings in China. A total of 15 medical buildings in Northeast China were selected. The satisfaction of the elderly in the medical building with the environment was investigated through questionnaires; the sound, light and heat environment in the medical building was measured by instruments. Using the regression analysis method, we get the systematic factors that affect the quality of life of the elderly, and some relevant policy suggestions are put forward. In addition, the influencing factors were classified and stratified. The analysis showed that the three main factors affecting the quality of life of the elderly are sound, light and heat. These three factors ensure that the elderly medical care at the same time to stabilize the elderly pension environment. The results showed that the sound pressure level (SPL) of the activity room of the medical building facing the street was generally higher than that of the medical building not facing the street. Most of the respondents are satisfied with the thermal environment of the activity room. This study provides a basis for improving the living environment of the elderly in the medical buildings in Northeast China. [ABSTRACT FROM AUTHOR]

As natural predators, owls fly with astonishing stealth due to the serrated feather morphology that produces advantageous flow characteristics. Traditionally, these serrations are tailored for airfoil edges with simple two-dimensional patterns, limiting their effect on noise reduction while negotiating tradeoffs in aerodynamic performance. Conversely, the intricately structured wings of cicadas have evolved for effective flapping, presenting a potential blueprint for alleviating these aerodynamic limitations. In this study, we formulate a synergistic design strategy that harmonizes noise suppression with aerodynamic efficiency by integrating the geometrical attributes of owl feathers and cicada forewings, culminating in a three-dimensional sinusoidal serration propeller topology that facilitates both silent and efficient flight. Experimental results show that our design yields a reduction in overall sound pressure levels by up to 5.5 dB and an increase in propulsive efficiency by over 20% compared to the current industry benchmark. Computational fluid dynamics simulations validate the efficacy of the bioinspired design in augmenting surface vorticity and suppressing noise generation across various flow regimes. This topology can advance the multifunctionality of aerodynamic surfaces for the development of quieter and more energy-saving aerial vehicles. This study unveils a synergistic bioinspired design, seamlessly merging owl feather and cicada wing geometries into propeller configurations. Authors achieve reduction in noise by up to 5.5 dB while boosting aerodynamic efficiency by over 20% compared to current industry standards. [ABSTRACT FROM AUTHOR]

Uniaxial compression tests and cyclic loading acoustic emission tests were conducted on 20%, 40%, 60%, 80%, dry and saturated muddy sandstone by using a creep impact loading system to investigate the mechanical properties and acoustic emission characteristics of soft rocks with different water contents under dynamic disturbance. The mechanical properties and acoustic emission characteristics of muddy sandstones at different water contents were analysed. Results of experimental studies show that water is a key factor in the mechanical properties of rocks, softening them, increasing their porosity, reducing their brittleness and increasing their plasticity. Under uniaxial compression, the macroscopic damage characteristics of the muddy sandstone change from mono-bevel shear damage and 'X' type conjugate bevel shear damage to a roadway bottom-drum type damage as the water content increases. Dynamic perturbation has a strengthening effect on the mechanical properties of samples with 60% and less water content, and a weakening effect on samples with 80% and more water content, but the weakening effect is not obvious. Macroscopic damage characteristics of dry samples remain unchanged, water samples from shear damage and tensile–shear composite damage gradually transformed into cleavage damage, until saturation transformation monoclinic shear damage. The evolution of acoustic emission energy and event number is mainly divided into four stages: loading stage (I), dynamic loading stage (II), yield failure stage (III), and post-peak stage (IV), the acoustic emission characteristics of the stages were different for different water contents. The characteristic value of acoustic emission key point frequency gradually decreases, and the damage degree of the specimen increases, corresponding to low water content—high main frequency—low damage and high water content—low main frequency—high damage. [ABSTRACT FROM AUTHOR]

Introduction: The aim of this study was to evaluate noise exposure to the operating room staff consisting of the surgeon, assistant, anaesthetist and Mako Product Specialist (MPS) during Mako robotic-arm assisted total knee arthroplasty (TKA) and total hip arthroplasty (THA). We aimed to determine whether employees were exposed to noise at or above a lower exposure action value (LEAV) set out by the Noise at Work Regulations 2005, Health and Safety Executive (HSE), UK. Materials and methods: We prospectively recorded intra-operative noise levels in Mako robotic-arm assisted TKA and THA over a period of two months using the MicW i436 connected to an iOS device (Apple), using the Sound Level Meter App (iOS) by the National Institute for Occupation Safety and Health (NIOSH). Data obtained was then used to calculate "worst case" daily exposure value to assess if sound levels were compliant with UK guidelines. Comparison between operating room staff groups was performed with ANOVA testing. Results: A total of 19 TKA and 11 THA operations were recorded. During TKA, for the primary surgeon and the assistant, the equivalent continuous sound pressure level (LAeq) was over 80 dB, exceeding the LEAV set out by the Noise at Work Regulations by HSE. During THA, the average LAeq and peak sound pressure levels did not exceed the LEAV. The calculated daily exposure for the primary surgeon in TKA was 82 dB. A Tukey post hoc test revealed that LAeq was statistically significantly lower in the anaesthetist and MPS (p <.001) compared to the primary surgeon and assistant in both TKA and THA. Conclusions: Operating room staff, particularly the primary surgeon and assistant are exposed to significant levels of noise during Mako robotic-arm assisted TKA and THA. Formal assessments should be performed to further assess the risk of noise induced hearing loss in robotic-arm assisted arthroplasty. [ABSTRACT FROM AUTHOR]

Directional sensing of underwater acoustic signals is vital in many areas, such as waterborne navigation systems, abyssal signal communication, and underwater sound source localization. Here, we propose an easy-to-make acoustic sensing metamaterial device, which is made of a bubble architecture with a line defect. Both numerical and experimental demonstrations show that an input-direction-sensitive response with an acoustic pressure enhancement factor ~ 13.9 was achieved approximately at the resonant frequency. Furthermore, enhanced waterborne acoustic sensing at different frequencies was realized by adjusting the volume of the defect cavity. This strategy provides an effective and feasible method for underwater weak signal detection and localization. [ABSTRACT FROM AUTHOR]

Compared to the conventional cellular cores, the cellular cores auxetic metamaterials with negative Poisson's ratios have unique mechanical deformation characteristics, superior strength to density ratio and high stiffness, both of which can be used to build lightweight sandwich constructions. The purpose of this study is to investigate the vibration acoustic response of porous functionally graded honeycomb sandwich plates with a negative Poisson's ratio (NPR). Under simply supported boundary conditions, the dynamic equation of the sandwich plate is derived based on the Hamilton principle, and the eigenvalue of the modal function matrix is coupled with the Navier method to obtain the natural frequency. The theoretical calculation results are compared with the finite element software COMSOL simulation results, so as to verify the validity and correctness of the theoretical model proposed in this paper. The far-field radiation sound pressure level of sandwich plate under point force loading is derived by Rayleigh integral theory. The correctness of the proposed model is verified by comparing the radiation sound pressure level calculated by the theoretical model with the results obtained by the finite element software simulation. The effects of porous functionally graded materials (FGM) and cellular structure parameters on the acoustic radiation characteristics of sandwich plates are discussed in detail. The results show that: The relative error between the theoretical results and the literature results is 5.43 %. Under the same conditions, the amplitude of the radiation sound pressure level (SPL) decreases by about 29.48 % in the low frequency stage, 28.9 % in the medium frequency stage and 11.08 % in the high frequency stage under the point excitation when the cellular side length is 6 mm compared with 8 mm in the low frequency stage. The movement trend and amplitude of the sandwich plate's emitted SPL are significantly impacted by changes in the characteristics of the cellular structure. [ABSTRACT FROM AUTHOR]

In this study, we investigated the effects of thermal–acoustic environments on human comfort in a cold region by focusing on Xi'an in China as a representative city. Four typical open spaces were identified within two universities, with one located in an urban area and the other in a suburban area. Surveys were conducted using questionnaires and environmental parameters were measured to assess thermal–acoustic perception. The physiological equivalent temperature (PET) and noise sound pressure levels were employed to measure the thermal–acoustic environments in the four open spaces. The results showed that the neutral PET was 19.1 °C in Xi'an from March to May, and the neutral temperature range was 14.9–23.4 °C. The preferred temperature was 20.0 °C. Acoustic sensation votes were lower in suburban areas than urban areas. Respondents in urban areas exhibited significantly higher sensitivity to the thermal and acoustic environments compared with those in suburban areas. Sensitivity to the thermal environment decreased as the environmental noise levels decreased. The temperature perceived as most suitable increased as the sensitivity to the thermal environment decreased. Acoustic comfort evaluations were generally higher in colder and warmer environments. Warmer environments heightened the sensitivity to the acoustic environment and this effect gradually decreased as the sound pressure levels increased. Thus, based on empirical analyses, we compared the effects of outdoor thermal–acoustic parameters on comfort to provide experimental data support for further outdoor thermal comfort research. [ABSTRACT FROM AUTHOR]

Bismuth telluride (Bi2Te3), due to its thermoelectric properties, is an interesting semiconducting material for optoelectronics and energy conversion devices; still, it has limited stability and durability. Under high pressure, we can fine-tune its performance, potentially enhancing its capabilities. The presented work uses the semi-automatic Reddy tube to explore the behavior of bismuth telluride under dynamic pressure. Commercially available bismuth telluride was purchased and subjected to different numbers of shock pulses of 100, 200, 300, and 400 with 2 MPa transient pressure and 864 K transient temperature. XRD, Raman, UV-DRS, PL, and SEM were used to characterize Bi2Te3 and shock-loaded Bi2Te3. The XRD and Raman study confirms that the Bi2Te3 underwent phase transition from Bi2Te3 to Bi4Te5 (rhombohedral to hexagonal) at 300 shock pulses. The optical property of Bi2Te3 was determined using UV-DRS and PL; the bandgap and PL intensity changed with respect to the number of shock pulses. A scanning electron microscope was used to analyze sample morphology. Our findings reveal the reversible phase transition of bismuth telluride from Bi2Te3 to Bi4Te5 under dynamic shock waves, something that has not been reported earlier. Using traditional synthesis methods, Bi4Te5 consume a lot of time, leading to impurities and problems of sample quality. Our results reveal that a rapid and reversible phase transition and unique response to dynamic shock waves will allow excellent technological applications without requiring lengthy and complex synthesis methods, offering enhanced stability and potential advancements in energy conversion devices. The process detailing how shock waves initiate the phase transition is explained. [ABSTRACT FROM AUTHOR]