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This paper focused on the effects of non-acoustic factors on community response, namely annoyance and activity disturbances due to road traffic noise. Most of previous surveys in Japan addressed community response to noise for detached houses rather than that for apartments. However, it is likely that the above-mentioned community response differed by sound insulation performance between detached houses and apartments. Using a social survey conducted in areas facing arterial roads in 2019 and 2020, we applied the micro data to cross-tabulation and logistic regression analysis. Calculating phi coefficient and odds ratio, we discussed the difference by housing types. [ABSTRACT FROM AUTHOR]

Determining the target characteristics of vehicle components for the road noise requires much development effort because component's characteristics are set through trial and error utilizing actual vehicles and FEMs. The purpose of this study is to construct a method that can determine the target characteristics without making a vehicle that achieves the target performance, in order to reduce the study time of road noise. This study focuses on drive point inertance. This paper investigates a method of constructing a machine learning model that can determine the target value of the wideband frequency response. [ABSTRACT FROM AUTHOR]

First of all, the definition of “Unit Mode” is a smallest unit component mode which has only one loop and cannot be decomposed any further. The resonance frequency of an unit mode is almost the same as that of whole system. An unit mode is a disassembly of eigenmodes of each part, and eigenmodes are obtained by assembling the unit modes. The energy correlated with the response of interest on unit modal coordinates is called “Power Flow”. By visualizing this, it is possible to draw a mode path diagram that shows vibration transmissions from the excitation point to the evaluation point. The path can be changed by shifting the eigenvalues. This paper introduces the concept of power flow and its application to vibration transmitted through the vehicle body. [ABSTRACT FROM AUTHOR]

Quietness has become one of the key performance requirements for many users of vacuum pumps. In responcse, we launched the new air-cooled dry pump 'NeoDry-G' series in 2022. 'NeoDry-G' series is significantly quieter than its predecessor, the 'NeoDry-E' series. This paper provides a brief introduction to the NeoDry-G series, detailing how the quietness was improved and how it was evaluated. [ABSTRACT FROM AUTHOR]

Road traffic noise is one of the most important issues. A more accurate prediction model is necessary to incorporate measures for reducing this noise. Current simulation models like the ASJ-RTN utilize fixed vehicle sound models. To enhance accuracy, an updated vehicle sound model, is recommended. This paper proposes a method for creating vehicle sound models with minimal measurements, applicable to all vehicle categories. Additionally, it presents a case study comparing the impact on exterior noise of a 100% electric drive hybrid system vehicle and an ICE vehicle, using the sound model developed through this method. [ABSTRACT FROM AUTHOR]

In recent years, commercial vehicles with leaf suspension has been demanded to be as quiet as passenger vehicles. Therefore, rear differential gear whine noise also should be reduced and not to be stick out from interior back ground noise. It is known that the gear whine noise is strongly influenced by resonance of leaf suspension and the resonance frequency varies widely. This paper reports control method of the vibration characteristics of leaf suspension by changing the contact position and stiffness between each leaf, which is the main factor of variation. Using this method, gear whine noise could be decreased effectively. [ABSTRACT FROM AUTHOR]

In recent years, the achievement of the environmental quality standards in areas facing roads has been improved. On the other hand, many residents along arterial roads are still annoyed by road traffic noise. In this paper, focusing on roadside environments of arterial roads, we try to develop a hierarchical evaluation structure model of dissatisfaction with the roadside environments based on the answers to open-ended questions of residents themselves. By deciphering the evaluation structure model, we can clarify the reasons for the dissatisfaction with road traffic noise and measures to resolve them and comprehend the position of road traffic noise in roadside environments. [ABSTRACT FROM AUTHOR]

To reduce road noise effectively, focusing on high contributing principal component (PC) modes is a well known method. Although, the difficulty of simultaneous measurement when applied to actual vehicle test is one of the issues. Therefore, a method was proposed to obtain the whole body PC modes by integrating the partial PC modes. In this paper we applied this method to an operational test data for each measurement group and obtained the whole body PC modes, the effectiveness of the proposed method for practical usage was proved. [ABSTRACT FROM AUTHOR]

This paper introduces a new active suspension system and discusses the application of the energy optimal control theory. In this new suspension system, an actuator and a damper are arranged in series. Thanks to this new design, the suspension system without an additional mass consists of an active mass-damper system. Applying the energy optimal control theory, it is shown by-the computer simulations that the riding comfort can be improved over wide range of frequency including the resonance frequency of the unsprung mass. The results show that the vibration of the sprung mass is reduced to a level which is lower than that of a Shinkansen car without causing an increase in the vibration of the unsprung mass. Additionally, the control law is interpreted and the mechanism behind the decrease in the vibration of the sprung mass is analyzed. [ABSTRACT FROM AUTHOR]

This paper compares the characteristics of in-cylinder pressure measured in actual engines for various combustion modes and the characteristics of flame distribution and fuel reaction rate due to flame propagation calculated by CFD for those same modes, based on previous research. Results show that the significant increase in high-frequency in-cylinder pressure oscillation in pre-chamber jet combustion is due to two factors: a high in-cylinder pressure rise rate that is 2 to 3 times higher than in conventional spark ignition combustion, and an asymmetrical flame distribution caused by differences in fuel reaction rate of jet flames ejected from multiple nozzles of the pre-chamber. [ABSTRACT FROM AUTHOR]

In this paper, an evaluation method for in-cylinder pressure oscillation is developed to quantitatively determine the magnitude of combustion noise in the 7-10 kHz band characteristic of pre-chamber jet combustion engines. In this method, in-cylinder pressure is measured for 400 cycles of crank angle history, and peak-to-peak amplitudes of pressure oscillations in the combustion chamber resonance band are obtained for cycleby-cycle using a bandpass filter. The peak-to-peak amplitudes are then averaged to obtain an evaluation indicator for in-cylinder pressure oscillation that enables an indirect evaluation of high-frequency combustion noise without measuring engine radiation noise. The results showed that the evaluation indicator in pre-chamber jet combustion is 16 times higher than that of conventional spark-ignited combustion, which can be evaluated at a single fixed in-cylinder pressure sensor. [ABSTRACT FROM AUTHOR]

This paper analyzes the mechanism of vibrational energy propagation and panel vibration generation at the point joints between frame and panel which can be applied to reduce the noise. First, it is shown that the transmitted power at point joints that contribute to the panel vibration is caused by the out-of-plane component in relation to the frame deformation, and the evaluation of the out-of-plane transmitted power makes it possible to identify the effective site for reducing the panel vibration. Next, the relationship between the energy inflow to the panel and the panel vibration during the initial propagation of the traveling wave was numerically verified, and a panel vibration reduction method was proposed by suppressing the energy propagation to the panel. [ABSTRACT FROM AUTHOR]

This paper describes the vibration phenomenon on vehicle motion from the perspective of energy propagation based on a two-degree-of-freedom vibration system. The energy transmissibility between the yaw and roll motions is analytically formulated by using their uncoupled natural angular frequencies, damping, and coupling characteristics. It is shown that the neutral steering character can be expressed by zero-energy transfer between the yaw and roll motion. The transmissibility is also useful to express the transient performance of the vehicle with under/over steering characteristics and the stable limit speed and so on. Finally, it is demonstrated that the transmissibility is useful to understand the transient performance under changing the roll stiffness and damping coefficient as examples. [ABSTRACT FROM AUTHOR]

Since the large-scale construction of wind power facilities in Japan, serious complaints have arisen from residents regarding wind turbine noise (WTN). However, there was insufficient scientific background to assess this issue. To address this situation, several research projects have been conducted by the Ministry of the Environment, Government of Japan. In this paper, we report actual WTN field measurements for these projects. The L Aeq values of WTN ranged from 25 to 50 dB in residential areas. On the other hand, the residual noise levels in control areas with similar local characteristics to the wind farm areas but not affected by WTN ranged from 20 to 35 dB. Thus, there was a notable difference between WTN and residual noise. Wind power facilities are often constructed in quiet, rural districts. With regards to WTN, L Aeq of noise caused by wind turbines as well as the increase in the overall noise level are important. The measurements of spectral characteristics of WTN were compared against the criterion curve to assess low-frequency noise. As a result, infrasound (frequency components below 20 Hz) for all measured WTN values in the residential (immission) areas were found to be much lower than the corresponding values on the criterion curve. In addition, amplitude modulation (AM) sound (also referred to as "swish sound") is often associated with WTN, and can cause serious discomfort to nearby residents. The actual situation with regard to AM sound in residential areas located near wind farms was clarified by field measurements.

Objectives　Due to its' environment-friendly and clean energy characteristics, wind power has been increasingly used globally, particularly in advanced countries. However, concerns about health hazards, especially due to low-frequency and other noises generated from wind turbines, have been reported repeatedly. In order to manage adverse health effects appropriately, regulatory standards or guidelines that consider the health of residents need to be developed. To provide a scientific basis for the development of such regulatory standards and guidelines, this paper conducted a literature review to analyze epidemiological studies involving residents living in the vicinity of wind farms.Methods　Using the PubMED database, epidemiological papers that examined the health effects of noises produced by wind turbines were searched and collected. Additional papers were collected from the abstracts presented at relevant international academic conferences such as the Inter-Noise 2013 and Wind Turbine Noise 2015. An evidence table comprising the study design, subjects, exposure assessment, outcomes, confounders, and research results of each selected study was created.Results　A total of 11 papers were collected (2 of which were abstracts from the international academic conferences). These studies reported outcomes such as perception of noises, annoyance caused by the noises, and the association of the noises with stress and sleeplessness. Significant associations between the noises or annoyance produced by wind turbines and subjective adverse health effects were reported repeatedly. Two studies reported an odds ratio of 1.1 for an increase of 1 dB in the A-weighted sound pressure level as a factor representing the influence level. For other factors, it was not possible to compare the magnitude of the impact among the collected studies. Individual attitudes toward wind power and landscapes, economic benefits of wind farms, visibility of wind turbines, sensitivity to sounds, and concerns over health hazards were reported as confounders.Conclusion　Significant associations between the noises or annoyance produced by wind turbines and subjective adverse health effects were reported repeatedly. However, there was insufficient evidence to conclude whether the annoyance was caused by the psychological response to the construction of wind farms or by the actual exposure to noises generated by wind farms.

In order to improve wind noise in high frequency range above 2kHz, this paper proposes a new technique focusing on high damping glass-run to reduce glass transmission noise due to coincidence effect at low cost. The technique is characterized by controlling energy transmission by utilizing impedance matching between glass and glass-run without changing materials. [ABSTRACT FROM AUTHOR]

When a drone is used to suspend and transport a load, the residual vibration that occurs when the drone stops is a problem. In this report, residual vibration is suppressed by elimination of the natural frequency component from the apparent external force, which considers the effects of non-linearity and damping. Numerical simulations and experiments have verified the effectiveness of this method for a suspended load of a multi-rotor drone. [ABSTRACT FROM AUTHOR]

This paper addresses the cascading design method of NVH (Noise, Vibration and Harshness) performance between an OEM (Original Equipment Manufacturer) and suppliers. The increasing trend toward electric vehicles requires the exploring of cascading design method, because of the easiness of the assembly of the electric vehicles. However, there are difficulties for the cascading design of NVH performance to overcome the coupling problem among each subsystem. It is generally difficult to divide key evaluation characteristics of a whole structure to individual characteristics of each subsystem because of the coupling resonance. In this paper, cascading design method which utilizes the MMC (Mutual Mean Compliance) was proposed. The MMC is used as an index to meet the final NVH target levels of a whole structure. Then, the MMC is cascaded to each subsystem or component. Finally, the cascaded MMC is achieved by improving individual MMCs of each separate subsystem, while being careful about the resonance of a whole structure caused by strong coupling. In the paper, it is shown that the recalculation of MMCs after subsystem’s structural modification is feasible using FBS (Frequency response function Based Sub-structuring). In addition, MMC based cascading design method using FBS was defined and organized as a procedure. The method was also verified by a numerical case study.

The outboard motor market is expanding due to an increase in leisure use, and there is a demand for enhanced quietness and comfort of outboard motors. In the development of automobiles and motorcycles, original sound quality index research and sound quality development are being pursued to enhanced product value, but in the development of outboard motors, there are examples of noise reduction and compliance with noise regulations, but there are almost no examples of sound quality enhancement. In this study, we focused on the sound quality of outboard motors and conducted a questionnaire survey of North American boat users using the SD method. The difference in the impression of outboard motor sound quality was clarified, and factors affecting the results were obtained by factor analysis, and three important factors for sound quality of outboard motor could be extracted. In addition, considered the physical features of the extracted factors. [ABSTRACT FROM AUTHOR]

This paper discusses component mode synthesis (CMS) to solve the complex eigenvalue problem that expresses the disk brake squeal equation. The disk brake squeal is known as self-excited vibration; the real and imaginary parts of the complex eigenvalue indicate the damping coefficient and natural angular frequency, respectively. The modes that have a negative damping coefficient cause disk brake squeal. Therefore, calculating the eigenpairs (eigenvalues and eigenmodes) with accuracy is important. To solve the complex eigenvalue problem, a direct solver, such as the Hessenberg method, and an iterative solver, such as the Lanczos method, are used. By using a direct solver, all eigenpairs can be calculated with high accuracy, but the computational cost is large. Consequently, its application is limited to small DOF problems of approximately 10,000 DOF. On the other hand, calculating the eigenpairs of large DOF problems by using an iterative solver is possible; this also has disadvantages, such as missing actual modes and accepting quasi-modes. To overcome these disadvantages, a CMS that uses both a direct solver and an iterative solver is used. By using CMS, avoiding the disadvantages of missing actual modes and accepting quasi-modes while still using fewer computer resources than the direct solver alone is possible. However, the calculated eigenpairs contain computational error caused by CMS. In this paper, to improve the accuracy of CMS, a novel CMS method adapting residual stiffness is proposed. Here, novel CMS is formulated, and the advantage it offers is shown by applying the direct solver, the previous CMS, and the novel CMS to the finite element models of a disk brake.

Since the noise generated by mechanical structures affects the merchantability, it is important to predict it at the design stage. Statistical energy analysis (SEA), which solves the energy equilibrium equation between subsystems, is widely used to predict structural noise. However, due to the assumption that eigenmodes are treated statistically, SEA is limited to application in the high-frequency range with high mode density, so it is the challenge to develop vibration power flow analysis method for the low- and mid-frequency range. In this study, we propose a modal energy propagation analysis method to evaluate the vibration power flow between the eigenmodes of a subsystem. In this paper, the validity of the theory and the countermeasures to reduce the vibration by controlling the transmitted power between the eigenmodes are verified using a simple test apparatus. As a result, it was shown that the transmitted power between subsystems can be approximated by the summation of the transmitted powers of individual eigenmodes, confirming the validity of the calculation theory. In addition, it was confirmed that the mean square velocity of the subsystem can be reduced by identifying and controlling the transmitted power of individual eigenmodes using this method.

Noise in weaving mills has become very serious problem with increasing speed of weaving machine in recent years. One of these sources of noise is the collision sound of healds caused by shedding motion. It was clarified in our previous paper that the collision sound of healds is significantly connected with motion of heald during a period of shedding motion. In this research, therefore, photographs of the behavior of heald in a shedding period were taken by using a high-speed-camera system on a model shedding device. At the same time, noise was measured to investigate the collision sound of healds. Collision between healds and heald bar caused by heald jumping and the collision of healds were observed. It was confirmed that noise is the largest at the both collision timings. On the other hand, it has been already understood that the tension of warp yarn significantly affects the behavior of heald. It was also observed that the collision of heald and heald bar was delayed or eliminated with increasing tension of warp yarn by photographic observation. At the same time, noise was decreased with increasing warp tension. [ABSTRACT FROM AUTHOR]

In the automobile industry, quietness has been pursued with electrification and vehicle weight has been reduced for longer traveling distance. In design of component products to be mounted on vehicles, “low noise” and “weight reduction” have been also required. In order to realize them, it is important to approach sound characteristics in initial design stage and detail design stage. In the initial design stage, parts layout, material and rough dimensions are designed to decrease “average” of noise level. In the detail design stage, accurate dimensions and detailed shapes are designed to suppress noise peaks. These are called “two-step design”. Especially, analytical SEA (ASEA) is a suitable technology for the initial design because it provides results by using only theoretical equations without 3-D models. However, it has hurdles to be a practical process. One is a constraint of ASEA that accuracy of results can be kept high only in high frequency range. In this paper, we proved theoretically and practically that initial design using ASEA was effective even in low frequency range.

Statistical energy analysis (SEA) is a method for understanding energy transfer paths related to vibration noise generation. In SEA, a target object is separated virtually into subsystems among which the transfer of vibration energy can be quantified. Conventionally, SEA is applied to structures that comprise thin plates, such as the bodies of large ships. The structure is then designed so that the transfer of vibration energy is varied to avoid energy being concentrated on any one subsystem. Although SEA is an effective method for preventing vibration noise problems, it becomes critically inaccurate when applied to structures with low modal density. This paper is aimed at clarifying an appropriate measuring process for constructing SEA models with two subsystems that provides high accuracy for structures with arbitrary modal densities. Evaluations of three simplified structures with different modal densities are conducted to determine how to improve the conventional measurement method.

There are several types of sound localization methods. In middle frequency around 1kHz, these methods are effective to detect the sound source location. However, for low frequency sound under 100Hz, almost sound localization methods do not have enough resolution to detect the sound source location. To overcome this problem, the author is now developing a new sound localization method, "Double Near-field Acoustic Holography method." This method is converted method of conventional Near-field Acoustic Holography method. The Near-field Acoustic Holography method has best resolution in all sound localization method. However, for low frequency sound sources lower than 100Hz, this method does not have enough resolution to detect the its position. The proposed Double Near-field Acoustic holography method is developed to improve the resolution of low frequency sound localization. In this paper, the experimental results with small speaker are reported. By these experiments, it is probed that the proposed Double Near-field Acoustic holography method has enough resolution to detect the position of the low frequency sound source.

The aerodynamic noise generated from a perforated metal plate varied by air-flow direction. In the case of expansion type perforated metal plate, it generates very large level aerodynamic noise with a prominent peak in the frequency characteristic. In this paper, velocity fluctuation at some measuring points is measured by a hotwire anemometer to examine its cause. In the experiment, coherent output power (COP) of velocity fluctuation is calculated. The coherence function is defined by the relations between the generated noise and velocity fluctuation of air flow behind perforated metal plate. The expansion type perforated metal plate generates orderly vortex shedding and it brings the vibration of perforated metal plate. The distribution of partial overall value of COP indicates strong correlation with the plate vibration mode. That phenomenon is predicted as lock-in phenomenon between vortex and vibration of the plate.

Helmholtz resonators are used in many industrial products as devices for reducing low-frequency noise. An advantage of the Helmholtz resonator is that the structure is simple and applicable to low-frequency noise for its size. Further, an important feature is that the development costs and product costs are relatively low in actual product development. The optimum combination of the natural frequency and modal damping ratio of a Helmholtz resonator is dependent on the characteristic of the noise source. It is selected so as to minimize the sound pressure levels when the noise is stationary. In the case of a transient noise problem, the natural frequency and modal damping ratio is tuned for maximizing the modal damping ratios of the system consisting of the main system and a Helmholtz resonator. Noise reduction effects of Helmholtz resonators are generally predicted by 3D acoustic analysis. Recently, the effects are estimated by CFD at higher sound pressure levels exceeding 100dB, because they are greatly affected by eddies generated in the neck portion of resonators. However, there is no suitable method to predict the noise reduction effects of Helmholtz resonators that engineers can use easily in the early stages of design. This paper describes a simple method for estimating the optimum value of modal damping ratios of the acoustic system having a Helmholtz resonator. Here, two-degrees-of-freedom models similar to the mass-spring-damper models used in the design of tuned mass dampers are used. In addition, the differences between the optimum conditions of tuned mass dampers and Helmholtz resonators are described.

The present paper describes an application of non-parametric shape optimization to disc brake squeal phenomena. The disk brake squeal is known as self-excited vibration; the real and imaginary parts of the complex eigenvalue indicate the damping coefficient and natural angular frequency, respectively. The modes that have a negative damping coefficient cause disk brake squeal. Therefore, a main problem is defined as complex eigen value problem and a real part of the complex eigenvalue causing the brake squeal is chosen as an objective cost function for the shape optimization problem. For the solution to main problem which has a large number of DOF, component mode synthesis method adapting residual stiffness (CMS-R) is used in order to improve the accuracy of eigenpairs by conventional component mode synthesis method (CMS). The Fre´chet derivative of the objective cost function with respect to the domain variation, which we call the shape derivative of the objective cost function, is evaluated using the solution of the main problem and the adjoint problem. A scheme to solve the shape optimization problem is presented using an iterative algorithm based on the H1 gradient method for reshaping. For an application of the shape optimization method, a numerical example by using a practical disc brake model is presented. From the numerical result, the real part of the target complex eigenvalue monotonously decreases until it reach zero and effectiveness of CMS-R with regard to the shape optimization problem is presented.

In this paper, the phenomenon of vibration and noise in a small fan motor caused by electromagnetic forces were experimentally investigated. First, vibration characteristics of the fan motor in a non-operating state were determined by experimental modal analysis. Next, vibration and noise characteristics of the fan motor in an operating state were determined. The rotational speed was continuously decreased from 2200 r/min to 1200 r/min while the measurements were taken. A detailed frequency analysis was also performed to investigate the directional patterns of noise at the rotational speed which the significant resonance were confirmed. In addition, analysis on the vibration and noise of the fan motor after turning off its power were performed. As a result, it was found out that the significant vibration and noise were generated in the axial direction, and were resonance phenomena between harmonic frequency of electromagnetic force and natural frequency of the fan.

In this paper, a new method to evaluate performance of sound insulating plates in closed medium is investigated by using acoustic finite element method (FEM) under such two conditions that plates are having free ends and that plates are simply supported. The proposed method is able to compute sound transmission loss by using sound pressures at the small numbers of properly selected nodes considering acoustical symmetry of modal shapes in the closed medium, which is equivalent to the theoretical transmission loss without using all nodes existing in the medium. By the proposed method, the computed transmission loss does not depend on sizes or shapes of the medium; it is the unique transmission loss of the sound insulating plate itself. As sound insulating plates, the following three models are constructed; a single plate, double-leaf plates and the high-rigid sandwich panel called “trusscore panel”. It is also shown that sandwich trusscore panel works effectively at low frequency range since it is sufficiently rigid and that computed sound transmission loss of the trusscore panel has tendency as observed on a single plate having the equivalent weight and stiffness to the trusscore panel. Trusscore panels can be applied widely in industrial fields in the future such as walls or floors in a car, train or building to reduce interior noise.