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The study aims to diagnose the sound pressure levels inside incubators in a controlled environment under free-field conditions. The tests were carried out in a semi-anechoic room under the standard UNE-EN ISO 3745:2012/A1:2018 in three different operating states: off, on, and on with a temperature alarm triggered. Sound pressure levels were analyzed in three different models of incubators, both inside and outside. The main noise indices analyzed were the corrected equivalent continuous level (LKeq) and the equivalent continuous level (Leq) in third-octave bands. The results obtained under normal operating conditions showed variations among the different incubators, with overall values between 48.8 and 56.3 dBA. The influence of the alarm considerably worsened these data. The values obtained showed that premature newborns are exposed to noise levels above international recommendations. All incubators tested showed the presence of tonal components, both outside and inside the incubator cabin, and, in some cases, low-frequency components, but no impulsivity components were observed in any case.

In speaking, shouting, and singing, vocal loudness is known to be regulated with lung pressure, but the degree to which vocal fold adduction and airway shape play a role in loudness control is less well known. When loudness is quantified in sones instead of sound pressure level (SPL), the regulatory mechanisms are even less obvious. Here it is shown computationally that loudness is insensitive to changes in SPL produced with variable adduction. A trade-off exists between a reduction in glottal flow amplitude and a flatter spectral slope. When the airway configuration is changed from a uniform tube to a "belt" or "call" shape, loudness can increase with a slight decrease in SPL. When the airway configuration is changed from a uniform tube to an operatic "ring" shape, loudness is increased with only a small increase in SPL.

Summary Objectives/Hypothesis The purpose of this study was to determine the relationships among cognitive loading, autonomic arousal, and acoustic measures of voice in healthy older adults. Study Design Prospective and observational. Methods Twelve healthy older adults (six females) produced a sentence containing an embedded Stroop task in each of two cognitive load conditions: congruent and incongruent. Three physiologic measures of autonomic arousal (pulse volume amplitude, pulse period, and skin conductance response amplitude) and four acoustic measures of voice (cepstral peak prominence, low-to-high spectral energy ratio, fundamental frequency, and sound pressure level) were analyzed in each cognitive load condition. Results A logistic regression model was used to predict the cognitive load condition using participant as a categorical predictor and the four acoustic measures and three autonomic measures as continuous predictors. Skin conductance response amplitude and pulse volume amplitude were both predictive of cognitive load; however, no acoustic measures of voice were statistically significant predictors of cognitive load for older adults. Conclusions These findings support the idea that increased cognitive load is associated with increased autonomic nervous system activity in older adults. The lack of changes in acoustic measures of voice with increased cognitive load may result from age-related changes in vocal quality and speech subsystems.

Background: It is known that high noise levels can be harmful to preterm infants, causing physiological and psychological disorders. It is also known that premature babies spend a lot of time in an incubator. In this sense, many studies show that incubator noise levels can range from 45 dB to 70 dB. However, these differences in noise levels depend, fundamentally, on the methodology used, which a very varied.This study aims to know the levels of noise from a fan in the incubator itself and how much can isolate the noises coming from the outside.Methods: It was character was the acoustic behavior of several models of incubators. For this purpose, it was measured the incubator’s noise level within an Sound-dampened booth for free-field audiometry. It also used a 4224 pink noise generating source to determine the isolation levels of the incubators and one microphone inside the incubator and another one outside connect to an SVAN958 noise analyzer.Results: The incubators produced continuous equivalent noise levels of between 53.5 dB and 58 dB. The analysis of isolation showed that the level varied from one incubator to another, between 5.2 dB and 10.4 dB. In addition, the isolation level in one-third octave bands varied from one incubator model to another.Conclusions: Preterm infants in an incubator are exposed to noise levels very far from the international recommendations, even if the incubators are meeting the noise criteria set out in the IEC60601-2-19: 2009 standard of 60 dBA under normal use conditions.

Methods for measuring the acoustic characteristics of orifices have been reviewed. Comparison of three methods for evaluating of oscillation velocity in the neck of the Helmholtz resonator are presented. The first method is measurements in an impedance tube with the two-microphone method, the second is based on measuring the sound pressure in the resonator chamber, and the third is based on direct measurements of bias flow with a Pitot tube. The results of measuring the oscillation velocity in the neck of the Helmholtz resonator are presented, and show that these methods are in good agreement only within linear acoustics, but they lead to different results in nonlinear regimes characterized by high sound pressure levels.

In this study, based on a closed bomb test combined with computational fluid dynamics, a structural finite element method, and an acoustic boundary element method, a fluid-solid acoustic one-way coupling calculation model is established for the combustion process of energetic materials in a closed bomb, and the effectiveness of the model is verified by experiments. It is found that the maximum peak sound pressure increases exponentially with an increase in loading doses or gas pressure. However, a change in the combustion coefficient of the energetic materials has little effect on the noise generated during the combustion process in the closed bomb. When the combustion coefficient is reduced by a multiple of 16, the maximum transient sound pressure is reduced by 1.79 dB, and the sound pressure level in the frequency band is reduced by 1.75 dB. With an increase in shell thickness, the combustion noise of the energetic materials in the closed bomb decreases, and the reduction range of the combustion noise increases with the increase in shell thickness.

Back-projection (BP) algorithm is a common image reconstruction algorithm for microwave-induced thermoacoustic tomography (MITAT). According to the thermoacoustic (TA) signals obtained, which are superimposed with the corresponding time inversion of each pixel in the region of interest (ROI), the BP algorithm can function in a quick response and is suitable for a fast real-time MITAT system reconstruction. However, high artifacts and background noises which can be caused by incomplete sampling of TA signals seriously affect the image quality. Method: In this paper, a multiple back-projection with impact factor (MBP-IF) algorithm based on circular scanning is proposed to solve this problem. Compared with the BP algorithm, the MBP-IF method calculates not only the initial acoustic pressure of the TA signal of each pixel, but also the complete acoustic pressure distribution at different moments of the thermoacoustic wave transmission, which based on the derivation of time. Then the influencing factors can be obtained which can effectively suppress artifacts and eliminate noises. Results: Through numerical simulation and phantom experiments, the MBP-IF algorithm has excellent advantages in suppressing image artifacts and noises. The method of image quantification is also used to verify this conclusion. Clinical or Biological Impact: In addition, due to the independence of acoustic pressure distribution at different time, the MBP-IF can be computing in parallel with GPU, which can be widely used in real-time medical clinical MITAT system construction.

Marine propellers have complex geometry and their performance is determined by costly and time consuming open water experiments. Use of numerical techniques helps researchers in effective design of propellers. Several approaches are used that predicted either hydrodynamic and acoustic response or structural response. Two-way fluid-structure interaction (FSI) analysis is a very useful approach providing all three responses which helps in the design, analysis and optimization of a propeller. The objective of this paper is to predict the hydro-elastic response of a propeller using two-way FSI on a 0.2m diameter, DTMB-4119 propeller using ANSYS software. Two-way FSI analysis is carried out using system coupling approach that transfers the data between the structural and fluid solvers. The turbulence effects are captured using the large-eddy simulation (LES) model and the Ffowcs Williams Hawkings (FWH) acoustic model is used for evaluating the sound pressure level (SPL) generated by propeller. Analysis is extended to evaluate the hydro-elastic and acoustic response of the propeller after validating the hydrodynamic performance with the experimental result in the literature. The results from Two-way FSI analysis are in close agreement when compared with the one-way FSI analysis. Two-way FSI can accommodate the peak value of stress and deformation developed during the initial part of the transient solution which is important in the design of propeller. This study reveals that metallic (NAB) propeller can be replaced by a composite propeller. The acoustic response from two-way FSI analysis will be more realistic due to the consideration of hydro-elastic effect of propeller.

One of the largest problems with electric vehicles is that they often go unnoticed by pedestrians due to the absence of noticeable noise generated by electric motors, which is a potential cause of accidents and collisions. Surprisingly, this positive property in terms of reducing the noise pollution is in fact becoming a road safety problem. In addition, with the promotion of electric traction vehicles due to new environmental policies and the current proliferation of personal mobility vehicles, this problem could even be increased in the coming years. Therefore, the future global road regulation has included aspects on noise and warning sounds that electric vehicles must emit in the years to come. However, despite the requirements, no specific signal type or many other features have been established. Only the emission levels have been set (56-75 dB). Consequently, within the framework of this problem, this article evaluates the acoustic characteristics of the sound that should be emitted by electric vehicles so that pedestrians can easily detect them and the optimal sound pressure level they should emit to not unnecessarily raise noise pollution levels, concluding that the emission limits established are excessive in certain scenarios and that optimal warning sounds must be focused on electronically imitating combustion engine noises.

In this work, porous Si3N4 ceramics were successfully and ultrasonically soldered using Sn9Zn2Al solder through sonocapillary and cavitation. Si3N4 ceramics were first ultrasonically wetted and then soldered. The results show that porous Si3N4 ceramics can be wetted in the air within extreme short time of 10 s under ultrasonic. The capillary filling distance of the solder into the ceramic micro-channels achieves a value of 60 μm within 10 s and increases with prolonged ultrasonic time and high ultrasonic power. The infiltrated solder tightly bonded with the ceramic rod. The shear strength of the joint increases at prolonged ultrasonic time and becomes stable after 60 s. A geometric model is built to analyze the infiltration mechanism of the solder, and the result shows that the acoustic pressure inside the solder can reach 4 MPa, which is much higher than the pressure (0.32–1.4 MPa) needed for the sonocapillary action. The wetting mechanism of the solder to the ceramic is analyzed based on the cavitation bubble dynamics calculation. The high liquid velocity, pressure and temperature caused by the collapse of the cavitation bubble serve as the main factors that wet the ceramic.

Acoustic levitation is considered one of the most effective noncontact particle manipulation methods, along with aerodynamic, ferromagnetic, and optical levitation techniques. It is not restricted by the material properties of the target. However, existing acoustic levitation techniques have some drawbacks that limit their potential applications. Therefore, in this article, an innovative approach is proposed to manipulate objects more intuitively and freely. By taking advantage of the transition periods between the acoustic pulse trains and electrical driving signals, acoustic traps can be created by switching the acoustic focal spots rapidly. Since the high-energy-density points are not formed simultaneously, the computation of the acoustic field distribution with complicated mutual interference can be eliminated. Therefore, compared to the existing approaches that created acoustic traps by solving pressure distributions using iterative methods, the proposed method simplifies the computation of time delay and makes it possible to be solved even with a microcontroller. In this work, three experiments have been demonstrated successfully to prove the capability of the proposed method including lifting a Styrofoam sphere, transportation of a single target, and suspending two objects. Besides, simulations of the distributions of acoustic pressure, radiation force, and Gor'kov potential were conducted to confirm the presence of acoustic traps in the scenarios of lifting one and two objects. The proposed tactic should be considered effective since the results of the practical experiments and simulations support each other.

Transcranial focused ultrasound (tFUS) is a promising non-invasive technique for treating neurological and psychiatric disorders. One of the challenges for tFUS is the disruption of wave propagation through the skull. Consequently, despite the risks associated with exposure to ionizing radiation, computed tomography (CT) is required to estimate the acoustic transmission through the skull. This study aims to generate synthetic CT (sCT) from T1-weighted magnetic resonance imaging (MRI) and investigate its applicability to tFUS acoustic simulation. We trained a 3D conditional generative adversarial network (3D-cGAN) with 15 subjects. We then assessed image quality with 15 test subjects: mean absolute error (MAE) = 85.72± 9.50 HU (head) and 280.25±24.02 HU (skull), dice coefficient similarity (DSC) = 0.88±0.02 (skull). In terms of skull density ratio (SDR) and skull thickness (ST), no significant difference was found between sCT and real CT (rCT). When the acoustic simulation results of rCT and sCT were compared, the intracranial peak acoustic pressure ratio was found to be less than 4%, and the distance between focal points less than 1 mm.

To weaken the noise pollution of wet cooling towers, a large-scale wet cooling tower with a 660 MW unit is used as an example, and the water-splashing noise is measured in a field test. The sound source characteristics are determined based on the field test results, and the sound source surface is specified as the initial parameters of the simulation. Then, the noise propagation model for the wet cooling tower is established based on the ray-tracing method, with a maximum relative error of only 2.22 %. Two noise reduction schemes, vertical and curved sound barriers, are proposed based on this model. Furthermore, the noise reduction effects of two different types of sound barriers are investigated. Under identical conditions, the simulation reveals that the vertical sound barrier performs better than the curved sound barrier in terms of noise reduction. In addition, The results also show that a vertical sound barrier with a length of 90 meters, a height of 10 meters, and a distance of 15 meters from the tower is an optimal scenario, with an A-weighted sound pressure level (A-SPL) of just 42.08 dB(A). In summary, the noise problem associated with wet cooling towers may be effectively addressed in this instance.

Four-wheeler automotive vehicle is the basic need of people in today’s life all over the world. But the noise coming from the exhaust system is highly affecting the human health. Among all the noise produce in vehicle, exhaust system noise is maximum. Muffler is one such acoustic filter used for reducing this exhaust noise. Hybrid muffler is one type of muffler which combines the properties of both reactive muffler and dissipative muffler and it operates at wide frequency range. In this study an already existing muffler (Reactive type muffler) used in 91bhp, 6000 RPM four-cylinder petrol engine was optimized to hybrid muffler. Aerodynamic and acoustic performance parameters were the main performance parameter and were determined by CFD analysis and acoustic analysis. The existing reactive muffler of the four-cylinder petrol engine could be replaced by the hybrid muffler. Here the mufflers were designed in ANSYS design modular and analyses were performed in ANSYS Fluent and COMSOL software. CFD analysis was performed for the existing muffler and three other newly designed muffler by considering inlet velocity boundary condition at inlet velocity 40 m/s and 80 m/s. It was observed that increase in pressure drop (aerodynamic performance) in model 4, model 3 and model 2 is around 38%, 33.2% and 29% respectively. Again, from acoustic analysis the transmission loss (TL) in model 4 was observed to be 47 dB whereas in other models it was around 20 dB. Further it was observed that the sound pressure level from model 1 at the exit is around 75–78 dB whereas in model 4 it was observed to be around 45–50 dB at the exit. Hence from both the analysis it is concluded that model 4 which is hybrid type muffler is the most optimized muffler.

The tilted-angle standing surface acoustic wave (taSSAW) microfluidic device has become a powerful tool for biosample separation due to its biocompatibility and non-contact, label-free, and high-efficiency nature. Studying and modeling particle deflection in a microfluid environment containing a taSSAW field is essential in the design of robust taSSAW-based microfluidic devices. Here, we present a numerical model taking into consideration fluid viscous drag force and the acoustic radiation force induced by scattering of acoustic waves for the study of particle deflection. The reliability of the model is validated by comparing our predictions with data from existing literature. In order to support our prediction experimentally, we fabricated a taSSAW microfluidic chip using 128° YX LiNbO3, and the deflection results for 3- and 7-μm polystyrene microspheres concur with the numerical estimation. The effects on particle deflection by parameters such as pre-focusing, pre-focusing width, average flow velocity, acoustic pressure amplitude, tilted angle, and surface acoustic wave frequency on particle deflection are then analyzed. This model could be used to optimize the design and better understand the mechanism of taSSAW microfluidic devices.

This study aims to develop a multilayer hybrid passive material for noise control in automobile by coupling of open pore polyurethane foam and closed pore aluminium metallic foam. As a preliminary study the proposed configuration were tested in two microphone impedance tube method to quantify sound absorption coefficient as per ASTM E-1050. Subsequently, the five useful input parameters used for Finite Element (FE) study is predicted by means of inverse characterization technique using Genetic Algorithm (GA). From the predicted values, equivalent porous material is modelled and coupled to test bench car model to evaluate the noise reduction capability in terms of overall sound pressure level. The results are made to compare with and without porous material conditions, also it indicate noise suppression of 5–20 dB in one-third octave band.

Summary Objectives This paper aims to study the effect of room acoustics and phonemes on the perception of loudness of one's own voice ( autophonic loudness) for a group of trained singers. Methods For a set of five phonemes, 20 singers vocalized over several autophonic loudness ratios, while maintaining pitch constancy over extreme voice levels, within five simulated rooms. Results There were statistically significant differences in the slope of the autophonic loudness function (logarithm of autophonic loudness as a function of voice sound pressure level) for the five phonemes, with slopes ranging from 1.3 (/a:/) to 2.0 (/z/). There was no significant variation in the autophonic loudness function slopes with variations in room acoustics. The autophonic room response , which represents a systematic decrease in voice levels with increasing levels of room reflections, was also studied, with some evidence found in support. Overall, the average slope of the autophonic room response for the three corner vowels (/a:/, /i:/, and /u:/) was −1.4 for medium autophonic loudness. Conclusions The findings relating to the slope of the autophonic loudness function are in agreement with the findings of previous studies where the sensorimotor mechanisms in regulating voice were shown to be more important in the perception of autophonic loudness than hearing of room acoustics. However, the role of room acoustics, in terms of the autophonic room response, is shown to be more complicated, requiring further inquiry. Overall, it is shown that autophonic loudness grows at more than twice the rate of loudness growth for sounds created outside the human body.

The aim of this study was to assess acoustically selected sacred buildings located in Szczecin. The research part contains the research methodology and the results obtained. The research was carried out using two methods. The first one is the integrated impulse response method, where, using a bursting balloon, the time of sound pressure drop was measured at selected points of the object. In the interrupted noise method, the sound pressure drop was measured after the noise generated by the omnidirectional loudspeaker had ceased. Reverberation time was calculated for the results obtained, which is the main and basic parameter determining the interior acoustics. On the basis of the above-mentioned measurements, the reverberation indicators for the temples were also calculated. When analyzing the components of the reverberation indicator, it was noticed that poor acoustics in the sanctuary concerns speech, while interior acoustics is good for the reception of organ music. In the analyzed church, the reception of liturgical music is also better than the reception of speech, but the differences between these values are small.

Human activities worldwide are increasingly releasing low-frequency noise into the environment. Anthropogenic noise imposes a novel stress for wild animals and has become an increasing global concern. Many animals have been found to mitigate noise disturbance by modifying their acoustic parameters, yet the calling behaviours of species that breed near airports have not been explored in detail, especially for amphibians. Here, we measured the environmental noise of a swamp close to the runway at Haikou Meilan Airport in China. We also recorded the calls of four anuran species that reproduce in this swamp, and we measured the sound pressure levels of each focal species. These frogs vary in their call amplitude and possess disparate spectral and temporal traits. We show that two frog species characterized by lower frequency calls increase their call frequency when an airplane takes off. Moreover, three anuran species characterized by higher call rates significantly reduce their call rates (or call efforts) in response to airplane flyby. These results suggest that animals’ behavioural adaptation to human-made noise may be species specific. Because call frequency and call effort have close relationships with reproductive success, we deduce that such noise-induced behaviour adjustments may influence the fitness of taxa that depend on communication by sound.

Noise and whole-body vibration measurements were made in a Viking military vehicle to determine the variation that should be expected during repeat measures, the effect of speed (up to 60 km/h in 5 km/h increments), and during travel over different types of terrain (comprising concrete road, gravel track and rough cross-country). Measurements were made at various crew positions (including the driver and commander) in both the front and the rear cabs in the vehicles. Three translational axes of vibration were measured in each seat. Two speeds were investigated over road (35 km/h and 55–60 km/h) and gravel (20 km/h and 35 km/h) surfaces. The effect of varying speed of the vehicle on the measured noise and vibration magnitudes was also investigated. The highest sound pressure level (LAeq) of 104 dB(A) was measured at the commander’s standing position during travel over concrete road at 55 km/h. Higher noise levels occurred for a standing commander compared with when sitting on the seat. A maximum single axis frequency-weighted vibration magnitude of 1.0 m/s2 r.m.s. was measured on the driver’s seat during travel over track at 35 km/h. Higher vibration magnitudes occurred during travel over track compared with travel over road. Both noise and vibration exposure of crew within the Viking vehicle increased with increasing speed of the vehicle.

This study investigates complex acoustical intensity using a polyvinylidene fluoride (PVDF) bimorph. Analytical models of the open-circuit voltage outputs of an infinite-strip-shaped PVDF bimorph cantilever in an underwater sound field are developed. Results show that the sound pressure generates the sum of the outputs, while the particle velocity normal to the PVDF surface generates the difference. The sensitivities of the pressure- and velocity-generated voltage responses with respect to an incident plane sound field demonstrate uniform directivity in a low-frequency range, which is suitable for acoustical intensity determination. The higher velocity sensitivity confirms the advantage of using a PVDF bimorph as a velocity sensor, owing to its light weight and flexibility. An algorithm for determining the complex acoustical intensity normal to the surface is proposed by utilizing those voltage responses and the probe gain calibrated with a given angle of incident sound. This algorithm allows accurate determination of sound intensity of a plane wave field, where the reactive part of intensity is absent. However, a small error may exist when the reactive intensity is large and active intensity is small. This small discrepancy arises from the inherent variation in the phase directivity of the gains, which decrease with frequency.

Flow-induced noise in the expansion device can be very disturbing. The thermal expansion valve is usually positioned near the occupants, often resulting in flow-induced noise that can be perceived as annoying. Current studies lack a quantitative relationship between flow characteristics and flow-induced noise. Therefore, in this paper, a noise prediction model is proposed to predict the sound pressure level of flow-induced noise. The study utilizes a pumped R134a loop for synchronized measurements between flow-induced noise and flow regimes. Synchronized high-speed measurements obtained from a microphone and a high-speed camera enable simultaneous investigation of flow-induced noise and flow regimes. In this case, the experimental results find a gurgling noise distributing near 9 kHz. Using the TXV inlet pressure for calculating thermodynamic properties, the gurgling noise sound pressure level prediction error is less than 15%. A hissing noise distributing at around 15 kHz is not as noticeable as the gurgling noise. The error of sound pressure level prediction for hissing noise is less than 40%. Both the experimental results and the modeling results show that the sound pressure level of gurgling noise increases as the vapor mass fraction increases or the system mass flux increases. From the experimental results, the noise waveforms are distinguished. The model can correctly outline the shape of noise waveforms for different flow regimes with the help of visualizations. The model introduced in this paper shows the proper prediction for flow-induced noise except for the annular flow entering the valve.

Anurans that breed in rivers and cascade streams need to deal with the influence of the low-frequency water flow noise that could interfere with their acoustic communication. To overcome that, some species display visual signals or emit high-pitched calls. However, there is a constraint related to body size [snout-vent length (SVL)] that limits the anurans' calling frequency range. Thus, to evaluate if water noise influences this allometric relationship, we analysed hylodid frogs’ SVL, dominant frequencies of advertisement call, and background noise to which individuals are submitted. Although Hylodes and Crossodactylus have differences in morphology and natural history, we found negative acoustic allometry in both genera. This allometry may be part of the explanation of the absence of advertisement calls in Megaelosia and Phantasmarana genera. Based on the large body lengths of Megaelosia and Phantasmarana species, if they could call, it would be low-pitched and acoustically masked by the stream noise. Besides, we found a positive relationship between Hylodes phyllodes advertisement call and background sound pressure level (SPL), thus, the analysed individuals, emitted louder calls when submitted to louder background SPLs. This study exemplifies the complexity of acoustic allometry in rheophilic species: we evidenced a strategy for intraspecific communication effectiveness in rivers and streams with broad water flow background noise; and how acoustic allometry coped with background noise could be implying in unexpected trait evolution, as lack of vocalization in anurans.

The purpose of this paper is to study the acoustic signal characteristics of a Ranque-Hilsch vortex tube and discuss the energy separation phenomenon behind it. Experiments were conducted with air as the working fluid. The acoustic signal and corresponding thermal fluid parameters are measured. The influencing factors such as inlet pressure, nozzle number, and cold mass fraction were investigated. The results show that the acoustic energy of the vortex tube is chiefly within the range from 4000 Hz to 5000 Hz. Two frequency peaks (about 1500 Hz and 4200 Hz) are observed in the frequency domain. As the inlet pressure increases, the sound pressure level(SPL) increases, and as the cold mass fraction increases, the SPL decreases. There is a positive correlation between the sound intensity and the energy separation performance. Interestingly, the vortex tube with 5 nozzles produces maximum SPL and COP (Coefficient of performance) compared to the 4-nozzle and 6-nozzle vortex tubes.

Acoustic manipulation is a non-contact process that applies acoustic waves to immobilize particles into a specific region for a variety of potential applications. This provides an alternative way to address air ventilation requirements where building systems are becoming smarter and more efficient. Development of such a process within confined spaces can incorporate microscopic interactions to filter aerosol-based particulate matter (PM). In real-engineering conditions, it is hard to filter sub-micron particles (0.25–1.0 μm) than super-micron particles (> 2.5 μm) by using low-grade filters. The objectives of this work are twofold. First, we propose a new acoustic-driven pre-filtering device (i.e., a U-shaped resonant acoustic chamber) that can improve the working efficiency of low-grade filters for capturing such particles. Second, the device can optimize spatial homogeneity to enhance the removal efficiency of airborne particles under lower sound intensity requirements. The U-shaped acoustic-driven device in the form of a resonant chamber allows PM to reside at the pressure node of a standing wave. Experimental studies are conducted to verify the present design. The results show that an overall filtration efficiency of up to 89% for 1.0-μm airborne particles can be achieved when the acoustic-driven device is coupled together with a low-grade MERV-6 coarse filter. As a standalone device, the acoustic effect works well for the sub-micron particles with a filtration efficiency of up to 61% under a lower sound pressure level (116 dB) than as previously reported in the literature. In the analysis, we also discuss the performance dependence on frequency, sound pressure level and flow rate in terms of particle size distribution. The relevance of this research is a major step towards engineering an acoustic-based pre-filtering technique for developing future innovative ventilation solutions.

Waveguides allow grating lobe free beamforming for air-coupled ultrasonic phased-arrays by reducing the effective inter-element spacing to half wavelength. Since the sound waves propagate through the waveguide ducts, additional time delays are introduced. In this work, we present analytical, numerical, and experimental methods to estimate these time delays. Afterwards, two different waveguides are compared. The first one consists of equal-length ducts, requiring a time-consuming assembly process of the ultrasonic phased-array. In contrast, the second waveguide consists of Bézier-shaped ducts of unequal lengths but a planar input port allowing fast assembly. The analytical model is based on the geometric lengths of the waveguide ducts. The numerical model relies on a transient finite element analysis. All simulations are validated in an anechoic chamber using a calibrated microphone. The analytical (7.6% deviation) and numerical (3.2% deviation) propagation time models are in good agreement with the measurements. By using the analyzed propagation times for the compensation of the unequal waveguide duct lengths, we restored the beamforming capability without significant sound pressure level (SPL) loss. This work shows the possibility of reduced transducer assembly time for waveguided air-coupled phased-arrays without a reduced SPL.

The sensitivity of an infinite-strip-shaped polyvinylidene fluoride (PVDF) film in an underwater plane sound field is analyzed in this paper. The high-frequency sensitivity is characterized by the resonances of the symmetrical in-plane stress modes with traction-free boundary conditions at the ends of the film and by the anti-resonances due to the superposition of the stress components. The low-frequency sensitivity exhibits a simple hydrostatic response. The directional property of the in-plane stress component, generated by the incident sound across the thickness, has two contributions. The first is from the aperture and dipolar functions of the incident sound pressure over the PVDF surfaces and at the two ends of the film. The second is from an amplitude modulation by an angle-dependent gain. The directional property of the in-plane stress component by the sound pressure at the two ends of the film is only controlled by the dipolar function, and that of the stress component in the thickness direction is only determined by the aperture function. The illustration of the frequency and directional features of the PVDF film may advance understanding of the mechanisms involved in generating the voltage output of PVDF by an incident sound field.

An optical wave microphone, which is well designed based on Fraunhofer diffraction of a laser beam, is expected to be applied to various acoustic fields where conventional microphones cannot be used due to strong electric and/or magnetic field. The authors have developed this technique and applied it to detect discharge sounds emitted from plasmas such as micro plasma, gliding arc plasma and plasma jet. An improved optical wave microphone with regard to signal-to-noise ratio uses single mode optical fibers for laser transformation. In this study, detailed characteristics of the fiber-type optical wave microphone were evaluated according to the theory of the optical wave microphone. Furthermore, the fiber-type optical wave microphone was combined with computer tomography (CT). The fiber-type optical wave microphone CT succeeded to visualize and quantify 2-D acoustic field generated by an ultrasonic transducer, and the obtained sound pressure distribution showed good similarity to that measured with a condenser microphone. Furthermore, the technique was applied to surface barrier discharge with different applied voltage frequencies and the distribution of acoustic waves above the discharge was quantified.

This article investigates the dependence of transmitting sensitivity on the top electrode design of piezoelectric micromachined ultrasonic transducers (PMUTs). Two typical top electrodes, namely inner electrode (IE) and outer electrode (OE), are designed and fabricated. The measured transmitting velocities of the fabricated PMUTs at resonance under a drive voltage of 5 $\text{V}_{\mathrm {p-p}}$ (peak-to-peak) are 15.36 mm/s for the IE design and 20.67 mm/s for the OE design with a circular diaphragm and 16.62 mm/s for the IE design and 22.18 mm/s for the OE design with a hexagonal diaphragm. The OE design demonstrates a transmitting velocity improvement of 34.57% for the circular diaphragm and 33.45% for the hexagonal diaphragm. The improvement is due to the fact that the OE design shows higher quality factor ( ${Q}$ ) than the IE counterpart. Moreover, the resonant frequency of the OE design is higher than that of the IE design, which results in a larger acoustic pressure output and hence higher transmitting sensitivity. This work highlights an effective and simple approach for PMUTs to achieve high transmitting sensitivity, which is an important parameter in the applications that require large sound pressures, such as fingerprint imaging, gesture recognition, and ranging.

In the event of fire, how quickly occupants can hear, see, and/or smell the fire and then exit the building are important for reducing the number of potential casualties. After a person or an automatic fire-detection system detects a fire, an installed emergency alarm system is used to alert building occupants about the fire. The emergency alarm system plays an important role in alerting the occupants to the fire by emitting a high-pitched sound when the fire is initially detected. Although bells and electronic sirens can both be used in fire-alarm systems, usually only bells are used in most commercial fire alarms except for a few fire extinguishers. Recently, however, the development of circuit integration technology and subsequent competitive pricing and improved performance have fostered an environment favorable for the widespread application of electronic sirens. However, because electronic sirens that emit various sounds will likely confuse building occupants used to hearing familiar-sounding conventional fire-alarm bells, electronic sirens must be engineered to sound like conventional fire-alarm bells. Therefore, in this study, experiments were conducted to measure the specific sound pressure and frequency characteristics of commercially available fire-alarm bells and electronic sirens, and their characteristics were reviewed. In addition, the differences between the bells and sirens were analyzed to develop a plan for supplementing warning sounds of electronic sirens.

This study proposed a transfer matrix with harmonic frequencies for a parametrically excited system. The proposed transfer matrix applied to noise and vibration of a helical gear system. Gears are part of the parametrically excited system because of mesh stiffness variation. The nonlinear equation of motion for gears was linearized to an equation with the excitation of harmonic frequencies. Transfer matrix with harmonic frequencies for gear vibration was derived. The helical gear system was modeled using a shaft-bearing-circular plate with helical gears. The assembled transfer matrix of the helical gear system was obtained. Moreover, the assembled transfer matrix with harmonic frequencies was used to investigate the effects of dynamic and noise characteristics of the helical gear system owing to axial excitation. Result showed that sound-pressure level was closely related to the first-harmonic plate displacement caused by the first-harmonic axial force. Significant peaks of sound pressure were closely related to the first-harmonic component and had some peaks in the second and third components. The proposed transfer matrix can easily show the contribution of the harmonic components.

A sound or a noise that accompanies wood machining processes is introduced by the tool rotation itself, by the friction of moving machine parts, or by wood-tool interaction. The sounds generated during machining with a circular saw could be analysed in order to monitor and possibly control the cutting process. Applying altered cutting parameters while cutting beech wood (Fagus sylvatica L.), which is the most common wood species in the Republic of Serbia, caused acoustic emissions that could be analysed throughout corresponding spectra. As shown in previous studies, altering the cutting parameters, e.g., the feed speed and tool override, resulted in variations in power consumption, surface roughness, and acoustic emission (or acoustic pressure). The aim of this paper was to provide a possible correlation between the applied cutting parameters and the acoustic emission spectra with respect to consumed power and the state of the machined surface. Along with acoustic emissions, the power consumption and surface roughness data were also acquired in order to make a possible relationship. By associating the idle circular saw acoustic spectra with background noise and comparing them with those obtained during machining, it was possible to indicate spectrum areas of particular interest for further analysis.

To quantify the intensity of automobile brake creep groan, both experimental and analytical studies are innovatively conducted on the friction-induced vibration and noise of the disc brake in this paper. Experimentally, three factors, brake disc initial temperature, terrain, and gear position, are comprehensively contemplated to design six different test conditions, based on which a creep groan vehicle road test is conducted. Depending on the subjective evaluation and statistical analysis of the annoyance degree caused by vibration and noise in the starting and braking process under different test conditions, the influence of each factor on creep groan intensity is obtained. By processing the brake caliper and lower suspension arm acceleration and the interior sound pressure signals acquired in the test, the occurrence conditions and transient dynamic characteristics of creep groan are explored. One of the creep groan vibration modes is triggered by the rapid removal of the force exerted on the brake pedal when the vehicle starts at an extremely low speed, which presents intermittent impact and chaotic characteristics. The other vibration mode shows periodic harmonic characteristics, whose energy is concentrated on specific frequencies in the form of frequency doubling. This vibration mode occurs when continuously maintaining a low brake oil pressure or slowly releasing the force exerted on the brake pedal during the vehicle low-speed starting process, the velocity-displacement phase-plane portrait of which shows a stable limit cycle of stick-slip motion. Analytically, four vibration indexes and four noise indexes are established to evaluate the intensity of creep groan, the validity of which is verified by linear regression analysis. Finally, by combining all effective indexes, multiple linear regression analysis is performed, based on which the mapping relationship between the subjective evaluation of creep groan and effective indexes is obtained. The results demonstrate that the combination of the logarithmic vibration dose value of maximum brake caliper acceleration pulse and the loudness of interior noise can accurately describe the annoying degree caused by creep groan. The regression model can quantify and predict creep groan intensity of the test vehicle under different test conditions, which has guiding significance for engineering applications.

A noise source characteristic of an unheated compressible jet is experimentally investigated for the jet with exit Mach number 0.8. Measurements of acoustic pressure fluctuations were performed in the near-field and far-field independently to identify noise source characteristics using the correlation technique. Near-field and far-field acoustic pressure fluctuations were also measured simultaneously to identify the acoustic component in near-field pressure fluctuations measured. Measurements were taken for the base and chevron nozzle with the nozzle exit diameter of 30 mm. From auto-correlation and cross-correlation in the near and far fields, it is observed that region surrounding to mixing layer is dominated by random small scale structures which radiate noise to sideline direction in the far-field. Correlation obtained at downstream of the potential core in the near-field represents the dominance of coherent large scale structure which radiates the noise to the far-field in the aft angle direction. Chevron changes the characteristics of noise sources. The size of the dominant large-scale noise source reduces due to chevron. Coherence of the noise source in the region surrounding to mixing layer reduces due to chevron which is responsible for reducing the energy of the dominant noise sources downstream of the potential core. Near-field far-field cross-correlation confirms that spatial near-field location for radiating acoustic pressure fluctuations more efficiently to the far-field at polar angle 30° is dependent on axial as well as transverse position in the near-field. Chevron reduces the convective velocity of the flow. Chevron also reduces the spatial correlation length scale of the dominant noise source. Chevron changes the acoustic pressure in the near-field thereby shifting the dominant noise source towards the nozzle exit.

This study illustrates the design, modeling and fabrication of a piezoelectric acoustic sensor based on ZnO to be utilized for aeroacoustic measurements. In aeroacoustics, measurement of high sound pressure level (SPL) (upto ∼ 180 dB) is a necessary prerequisite. The design of the device was accomplished through a combination of piezoelectric composite plate theory, lumped element modeling (LEM) and MEMS-CAD tool Coventorware. The optimization of Si-diaphragm thickness of the device for the desired SPL range was achieved by using Coventorware. Also, the cavity created after diaphragm development was connected to the outside environment via a microtunnel which was designed for low cut-off frequency. The complete frequency response of the device was determined from LEM using the simulation tool MATLAB. The low cut-off frequency, bandwidth and flat band sensitivity of the sensor have been found to be 48 Hz, 54 kHz and 130 μV/Pa respectively. The designed sensor was fabricated using standard Si-fabrication technology. The testing of the fabricated device was done using Laser Doppler Vibrometer (LDV). The resonance frequency obtained from LDV measurement has been found to be 99.6 kHz.

This paper is devoted to the robust optimization of nacelle liners (acoustic treatments). The full computational aeroacoustic model is based on the convected Helmholtz equation in presence of a non...

Existing models of extended-tube liners are mainly applicable to the normal-incidence case, and the influence of the grazing-flow effect is often ignored. In the current paper, an impedance model i...

A compact cantilever-based voice-eavesdropping microresonator is proposed. The dynamic vibration of the cantilever-microresonator system induced by an applied acoustic pressure is converted into a modulation of the cavity resonances. Then, the resonance-shift-induced optical transmission change is utilized to detect the applied acoustic signals. The enhancement of both the vibration and optical response makes the proposed system highly sensitive and have better performance than many other optical acoustic sensors. The noise equivalent pressure of the proposed system at 900 Hz is 52 μPa/Hz1/2. The system has a favorable broad frequency response range covering 0∼6 kHz. Experimental results prove that the system can acquire and reconstruct a voice signal 7 m away with high sensitivity and reliability, which can meet a variety of needs, such as indoor eavesdropping. Furthermore, the system is easy to fabricate, has low power consumption and is fairly tunable in terms of the frequency response range and sensitivity. This microcavity-based novel acoustic sensor is promising for opening up new possibilities in intrusion detection, voice eavesdropping and many other vibro-acoustic analysis applications.

Among the main problems affecting the sound pressure level (SPL) of piezoelectric microelectromechanical systems (MEMS) speakers is that the membrane vibration displacement of those with sealed membranes is small, while those with unsealed membranes suffer from acoustic loss. Presented here is a high-SPL piezoelectric MEMS speaker via a rigid-flexible coupling mechanism, which can maintain large vibration displacement of the unsealed membranes without acoustic loss. The ingenious deposition of Parylene C on the upper surface before etching the back cavity is the key process forming the rigid–flexible-coupling sealed vibration membrane. Compared with that of the proposed speaker without the flexible sealed Parylene C at 2 V, the SPL generated by that with the rigid–flexible-coupling sealed vibration membrane is 3.0–26.1% higher, the frequency range of the speaker with the sealed membrane is widened from 250 Hz–20 kHz to the human hearing frequency range of 20 Hz–20 kHz for SPLs exceeding 59 dB, and a 101.2-dB SPL is obtained at the resonance frequency of 6.7 kHz. This simple strategy represents a significant step toward practical applications of piezoelectric MEMS speakers, given the wide frequency band, high SPL, and low power consumption. [2021-0041]

Vertical-axis wind turbines are an attractive option for small-scale wind-power installations. In this application, noise is crucially important. To investigate the problem, measurements taken from a model-scale turbine in a wind tunnel are considered. The sound radiated by the model is clearly evident in the cross-spectra from a pair of flush-mounted microphones. Parameter studies show that, in the normal operating range, speed is the dominant factor. The main source appears to be blade self-noise, although there are also indications of blade-wake interaction in the downstream half of the rotation path. Boundary-layer trips have a significant impact, showing that laminar instability is an important contributor to the self-noise. It will remain a risk at full scale, and its absence should be ensured at the design stage. To minimize the remaining sound radiation (at a given wind speed), configurations with lower tip-speed ratio at maximum power output should be preferred to ones having higher values of this parameter.

The noise levels emitted by agricultural machines can be harmful to the worker's health, and it is sometimes neglected in rural areas. This work aimed to measure the sound pressure levels emitted by three agricultural tractors of different power activating two types of implements to assess whether there were risks to operators' health and the onlookers working around the tractor. The sound pressure level data were collected using a decibel meter in ten points on each machine side (forward, rear, left, and right) for a total of 40 points around each tractor. Three different tractors were evaluated in different scenarios: without any implement, coupling and activating a spreader, and coupling and activating a rotary hoe. The tractor was parked at the centre of the mash with an engine speed that ensured 540 r.p.m. to the power take-off (PTO) during the entire data collection. The data were analyzed by charts, linear regression, and hierarchical clustering analysis. The results indicated that the sound pressure levels in all of the studied situation exceed the standard's limits, making hearing protectors essential during the working day., Níveis de ruído emitidos por tratores agrícolas com e sem acionamento de implementos Os níveis de ruído emitidos pelas máquinas agrícolas podem ser prejudiciais à saúde do trabalhador e, por vezes, negligenciados no meio rural. Este trabalho teve como objetivo mensurar os níveis de ruído emitidos por três tratores agrícolas de diferentes potências acionando dois tipos de implementos para avaliar se havia riscos à saúde dos operadores e trabalhadores de apoio ao redor da operação. Os dados de ruído foram coletados por decibelímetro em dez pontos de cada lado da máquina (frente, trás, esquerda e direita) para um total de 40 pontos ao redor de cada trator. Três tratores diferentes foram avaliados em diferentes cenários: sem implemento, acoplando e acionando uma esparramadora de corretivo e acoplando e acionando uma enxada giratória. O trator foi estacionado no centro da mistura com uma rotação do motor que garantiu 540 rotações por minuto (RPM). para a tomada de potência (TDP) durante toda a coleta de dados. Os dados foram analisados ​​por meio de gráficos, regressão linear e análise de agrupamento hierárquico. Os resultados indicaram que os níveis de pressão sonora em todas as situações estudadas ultrapassam os limites da norma regulamentadora (NR) 15, tornando os protetores auditivos indispensáveis ​​durante a jornada de trabalho. Palavras-chave: ergonomia; conforto acústico; mecanização agrícola; nível de pressão sonora. ABSTRACT: The noise levels emitted by agricultural machines can be harmful to the worker's health, and it is sometimes neglected in rural areas. This work aimed to measure the noise level emitted by three agricultural tractors of different power activating two types of implements to assess whether there were risks to operators' health and the supporter workers around the tractor. The noise level data were collected using a decibel meter in ten points on each machine side (forward, rear, left, and right) for a total of 40 points around each tractor. Three different tractors were evaluated in different scenarios: without any implement, coupling and activating a spreader, and coupling and activating a rotary hoe. The tractor was parked at the centre of the mash with an engine speed that ensured 540 rotation per minute (RPM). to the power take-off (PTO) during the entire data collection. The data were analyzed by charts, linear regression, and hierarchical clustering analysis. The results indicated that the sound pressure levels in all of the studied situation exceed the standard's limits regulatory standard 15, making hearing protectors essential during the working day. Keywords: ergonomics; acoustic comfort; agricultural mechanization; sound pressure level.

To ascertain the influence of occupational exposure to SPL on the hearing threshold of indoor cycling (IC) instructors. This is a cross-sectional study involving eleven IC instructors at fitness centers in Guarapuava, PR, Brazil Questionnaires were applied to assess occupational characteristics and reported auditory and extra-auditory symptoms. The hearing threshold was evaluated by pure tone audiometry testing at seven moments: after 14 h of acoustic rest, and before and immediately after exposure to SPLs of 95, 85 and 75 dB(A), making a total of 77 measurements of the group of instructors. Differences in means were assessed using the Kruskal–Wallis test. The k-means and composition method was applied using principal component analysis to verify the main factors associated with the broadband multi-frequency measurement at the hearing threshold. The average bilateral hearing threshold showed a significant increase at the intensity of 95 dB(A), at all the tested frequencies (p

A topology optimization method for coupled vibro-acoustic problem based on hybrid finite element-wave based method is proposed. The hybrid finite element-wave based method is used to model the coupled free layer damping structure-acoustics system, and a gradient-based topology optimization formulation is developed by solid isotropic microstructures with penalization method, to obtain optimized layout of free layer damping with the objective of minimizing sound pressure in the acoustic cavity and with constraint defined as the amount of free layer damping. The adjoint variable method for the coupled vibro-acoustic model based on the hybrid finite element-wave based method is also derived as a part of the sensitivity analysis. Numerical example shows that the optimized distribution reduce sound pressure effectively and the calculation time of proposed method is less than the conventional method for topology optimization base on finite element method. Experimental results verify the accuracy of the hybrid finite element-wave based method and the effect of optimized damping material layout is also validated by experiment.

OBJECTIVE To estimate the equivalent threshold sound pressure levels (ETSPLs) for nine stimuli used today and in the future for universal newborn hearing screening and diagnostics delivered by the Interacoustics SnapPROBE™. DESIGN The Click and eight variants of the CE-Chirp® were included to establish ETSPLs when delivered by the SnapPROBE™. The short duration stimuli were presented at a 20/s repetition rate for about 1-2 s following the international standards for establishing ETSPLs. STUDY SAMPLE 50 ears from a total of 27 normal hearing young adult subjects (female/male = 16/11; age = 21-25 years, mean age = 23.1 years). RESULTS Peak-to-peak equivalent signal levels and root mean square signal levels (at 20/s repetition rate) for the nine stimuli are stated. CONCLUSIONS The ETSPLs are in alignment overall with those found in previous studies, while some levels are about 2-6 dB higher for this study compared to the Interacoustics Titan IOW probe and the ER-3A insert earphone. The results are relevant for present and future universal newborn hearing screening and diagnostics carried out with the SnapPROBE™ to ensure that correct stimulation levels are applied.

In this article, we present a high-performance aluminum nitride (AlN)-based microelectromechanical system (MEMS) hydrophone sensor, in which the sensing cells are designed and arranged as an innovative honeycomb architecture for achieving large acoustic pressure sensitivity and high fill-factor. An $8\times9$ array of $360~{\mu }\text{m}$ in characteristic size, 0.92-MHz MEMS hydrophone sensor is developed based on an AlN-on-cavity silicon-on-insulator (CSOI) platform. The size of the MEMS hydrophone sensor is 3.2 mm $\times3.2$ mm. The MEMS hydrophone sensor and its preamplification circuit are integrated on a printed circuit board and packaged together with an acoustically transparent material, in order to meet the stringent requirements of underwater applications. The packaged MEMS hydrophone is fully characterized through using an industry-standard hydrophone calibration instrument. The MEMS hydrophone achieves an acoustic pressure sensitivity of −178 dB (re: 1 V/ $\mu$ Pa), with a maximum nonlinearity of 0.1%, and a noise resolution of 58.7 dB (re: 1 $\mu$ Pa/Hz). The measurement results show that the reported MEMS hydrophone sensor with bioinspired honeycomb structure is compared favorable with advanced commercially available bulky hydrophones.

The paper investigates the sound-pressure and phase-gradient distribution in the deep sea along signal propagation paths in the near and far acoustic brightness fields, as well as in the shadow zone. It is shown that the field characteristics formed by leaky, trapped, and water modes differ significantly. It was found that in zones of interference maxima, the phase gradients are smooth and, by analogy with shallow water, can be described using the effective phase and group velocities. It is shown that the characteristics of the effective phase and group velocities for leaky and trapped modes with variations in distance, reception and emission depths, and sound pressure frequency are stable and determined by uniform invariant dependences on distance. Analytical relationships are proposed to describe these dependences. It was found that the values of the effective phase and group velocities in zones with dominant water modes are nearly equal to the average sound speed in water. Recommendations are given for applying the dependences of the effective phase and group velocities in direction-finding of noise sources.

A description of a program for computation of acoustic fields in 3D shallow-water waveguides of arbitrary form is presented. This program is a C++ implementation of a numerical solver of wide-angle mode parabolic equations. The user can specify sound speed distribution, bottom relief, and the structure of bottom layers via configuration files when performing acoustic field simulation. The output of the program consists of one or several horizontal cut planes of the acoustic pressure field at specified depths. One of the main advantages of the implemented method is its high computational efficiency. The developed program is open-source and available online. It can be of interest for specialists in different areas of ocean acoustics who perform the modeling of sound propagation in course of the solution of various practical problems.

Wake-ingesting propellers are attractive for low-speed propulsion due to their potential fuel savings and aircraft configuration benefits. Aeroacoustic concerns must be addressed for such installed...

A promising method of identifying conductors in the conditions of agricultural enterprises is the use of acoustic identification tools that allow it to be carried out without disconnecting electrical receivers from the network, without violating the insulation of the identified conductors. The design of devices for acoustic identification requires the development of a methodology for calculating the sound pressure level in conductors when an acoustic signal is applied to them, depending on such factors as the distance from the identification point to the signal source, the cross section and material of the conductor cores, its insulation material, and the frequency of the signal being supplied. (Research purpose) The research purpose is in developing a methodology for calculating the parameters of the propagation of acoustic signals in conductors when identifying them using acoustic signals. (Materials and methods) The article presents the analysis of existing methods for calculating the acoustic characteristics of solids. The article describes the developed methodology for calculating the parameters of acoustic signal propagation in conductors when identifying them using acoustic signals and tested it using practical tests. (Results and discussion) The main parameter of acoustic signals in conductors when they are identified by acoustic means is the sound pressure level. Authors have developed a method for calculating the sound pressure level in conductors, taking into account such factors as the length of the identified conductor, the frequency of the acoustic signal, the conductor cross-section, the speed of sound waves in conductive cores and insulating materials. The article presents practical experiments to test the applicability of the developed methodology. (Conclusions). To date, acoustic signals are not used to identify conductors, a method for calculating the sound pressure level in conductors has not been developed, taking into account various factors. Authors developed a methodology and performed theoretical calculations of the sound pressure level in the conductors. Based on the results of practical experiments with the use of a control and measuring device, the applicability of the proposed methodology was confirmed.

This study is aimed at predicting the characteristics of vibration and sound radiation of violins and understanding the relationships among the properties of its wood, vibration, and sound radiation. Numerical simulations of the vibration mode of a violin body are performed, and the sound radiated by it are analyzed using the finite element method. The geometry of a real violin is scanned using a micro-computed tomography scanner, and the orthotropic properties of spruce and maple, such as Young's modulus, rigidity modulus, and Poisson's ratio, are set as the parameters of the numerical simulation. The main vibration modes, such as A0 and center bout rotation, and the acoustic pressure level around the violin body are calculated. This paper describes the influence of the density and longitudinal stiffness on the eigenfrequencies and sound radiation.