Interior Noise Reduction Research Articles

The development of an AVAS for enhancing the robustness of acoustic performance and reducing interior noise in a cabin

All the electric vehicles are required to provide warning sound by AVAS (Acoustic Vehicle Alert System) for the safety of pedestrians. AVAS sound should satisfy the regulations outside a vehicle while noise caused by the AVAS should be maintained below a level inside a cabin. Nowadays, it becomes difficult to fulfill these goals since various sensors for automotive drive are newly introduced in the space where the AVAS is traditionally located and an open area to emit sound is decreased to improve an electric efficiency of a car. Since the AVAS performance is very sensitive to a small change of the cavity, the increased complexity of the cavity makes it more challenging to develop a robust AVAS. The purpose of this study is to suggest a new AVAS for enhancing the robustness of acoustic performance as well as reducing interior noise in a cabin. Firstly, a series of simulations are carried out to closely investigate various design factors of the AVAS. Secondly, the improved performance of the new AVAS is shown through tests and simulations. Thirdly, a method to decide the optimal speaker location is newly suggested by simultaneously considering crucial performance factors obtained from multiple vehicle level simulations.

Interior Noise Reduction Method of Pantograph Areas for High-speed Trains Based on Active Jet Technology

Interior Noise Reduction Method of Pantograph Areas for High-speed Trains Based on Active Jet Technology

UIO-66-NH2/polydopamine double coating modification on cotton fabric for sound absorption and noise reduction

Noise pollution greatly harms social and economic development and human health. Textiles are used frequently and are essential to the interior's sound absorption and noise reduction. In this study, a polydopamine layer with damping, noise reduction, and adhesion functions was first finished onto cotton fabrics using a deposition method, followed by uniform spraying of Metal-organic framework particles with porous sound absorption structures using an ultrasonic precision sprayer. The successful adhesion of dopamine and UIO-66-NH2 on the fiber surface was verified using characterization methods, and the parameters affecting the acoustic properties of the fabric were explored. The results show that MOFs and polydopamine improve fabrics' absorption and reduction of acoustic waves. This work confirms the successful application of the double coating of UIO-66-NH2 and dopamine in fabric sound absorption. It provides a method for designing and preparing acoustic protection textiles.

EXAMINATION OF NOISE INSULATION OF BUILDINGS ON THE EXAMPLE OF RESIDENTIAL COMPLEXES IN ASTANA

The study investigates the effectiveness of noise insulation measures implemented in residential complexes within the urban context of Astana. Noise pollution is a pressing issue in urban environments, affecting residents' quality of life and well-being. This research examines the noise insulation strategies employed in selected residential complexes, analyzing their impact on reducing interior noise levels. The study employs various measurement methods and evaluates the acoustic performance of different building materials and designs used in the construction of these complexes. The findings of this research contribute to a better understanding of noise insulation practices in the context of urban development, providing insights for future architectural design and construction guidelines aimed at enhancing living conditions and minimizing noise-related disturbances.

Active vibration control for reduction of interior noise caused by R-MDPS

This paper presents an active vibration control (AVC) to reduce the vibration of motor driven power steering (MDPS). The MDPS used in the experiment was R-MDPS, an MDPS connected to Rack Gear. When the R-MDPS generates vibration in the operating state, the vibration is transmitted through the subframe. The vibration transmitted through the subframe generates indoor noise and reduces the driving quality of the driver. To reduce vibration, the AVC was used by inserting an actuator between R-MDPS and subframe. The actuator used Piezo material is called a Piezo actuator. To select the location of the actuator, Transfer path analysis (TPA) was performed. the effect was confirmed by setting the main path to error point. The experiment was conducted for feasibility by connecting R-MDPS and subframe to a test bench manufactured in the laboratory. The algorithm used for vibration control used the Filtered-X Least Mean Square (FxLMS) algorithm and the control result was reduced from 4 to 5 dB. It is shown that proposed method is an effective vibration reduction effect of R-MDPS.

Feasibility of a new noise prediction method using vibration speakers to verification of interior noise reduction effects

To effectively reduce interior noise in railway vehicles, the effect of new noise-reduction measures must be pre-estimated before their implementation. We are developing a new method for interior noise prediction, using a vibration speaker to estimate the multiple-input multiple-output transfer functions from the acceleration of interior panels to the sound pressures at the evaluation points. In this paper, we verify the possibility and report on the feasibility of predicting the effect of interior noise reduction in railway vehicles when the vibrations of interior panels are reduced to improve quietness in the cabin. First, we conducted a vibration test using a vibration speaker on a Shinkansen test car to estimate the transfer functions from each interior panel to the noise evaluation point. Then, we conducted another vibration test to simulate the running condition, aiming to reproduce the interior noise. Finally, by assuming that the vibrations of the interior panels are reduced in the second vibration test, we show the feasibility of the proposed method to verify the noise-reduction effect by using it to predict the interior noise with vibration-reduction measures.

A Review of Studies on Heat Transfer in Buildings with Radiant Cooling Systems

Due to their benefits in interior thermal comfort, energy saving, and noise reduction, radiant cooling systems have received wide attention. Radiant cooling systems can be viewed as a part of buildings’ maintenance structure and a component of cooling systems, depending on their construction. This article reviews studies on heat exchange in rooms utilizing radiant cooling systems, including research on conduction in radiant system structures, system cooling loads, cooling capacity, heat transfer coefficients of cooling surfaces, buildings’ thermal performance, and radiant system control strategy, with the goal of maximizing the benefits of energy conservation. Few studies have examined how radiant cooling systems interact with the indoor environment; instead, earlier research has focused on the thermal performance of radiant cooling systems themselves. Although several investigations have noted variations between the operating dynamics of radiant systems and conventional air conditioning systems, the cause has not yet been identified and quantified. According to heat transfer theory, the authors suggest that additional research on the performance of radiant systems should consider the thermal properties of inactive surfaces and that buildings’ thermal inertia should be used to coordinate radiant system operation.

Active vibration control for reduction of interior noise caused by R-MDPS of electric power steering in electric vehicle

This paper presents a novel active vibration control (AVC) system for a motor driven power steering (MDPS) system to reduce interior noise in an electric vehicle. The novel control algorithm used for the AVC system is developed based on selection of two reference signals. One is the frequency modulation signal using the rotation speed of motor shaft of MDPS the other one is the band passed signal of acceleration measured on the major path structure identified by the blocked transfer path (BF-TPA). In addition, the piezo stack actuator is used for generation of control force of the AVC system in the frequency over 400 Hz. An MDPS system uses electronic power steering. An MDPS system attached to the rack gear of power steering system is called an R-MDPS. The vibration generated by the R-MDPS is transmitted to the car body through mounts attached onto the car subframe. Panel vibrations of car body are sources of vibroacoustic noise generated inside the car cabin. This vibracoustic noise is a structure-borne noise and causes passenger annoyance. The frequencies of the structure-borne noise measured inside the car cabin are 460 Hz and 920 Hz, which are the rotating frequency of the R-MDPS motor shaft and the second-order harmonic of the rotating speed of the motor shaft. To directly reduce the interior noise inside the car cabin, active noise control (ANC) has been used for the active cancellation of noises with frequencies less than 400 Hz. However, because the frequency of interior noise generated by the operation of the R-MDPS is higher than 400 Hz, AVC was employed in this study for the active cancellation of vibrations transmitted to the car body through the subframe mounts of the car. For application of AVC to the test car, the control force should be known. Therefore, the actuator for generating the control force should be inserted in the mount between the subframe and R-MDPS system. Installing the actuator in the test car is challenging because of the geometry limit of commercial cars. Hence, a test jig composed of an R-MDPS system and the subframe of the test car was developed and set up in the laboratory to study the applicability of AVC to R-MDPS. All investigations of AVC were performed using the test jig in the laboratory. The proposed method was successfully applied to the active cancellation of vibration at a target point on the subframe.

Structural Design and Optimization of Nonuniform Chiral Phononic Crystals for Vehicle Interior Noise Reduction

Phononic crystals (PnCs) with nonuniform and chiral design are developed and applied for the reduction of vehicle interior noise. To investigate the effects of structural parameters such as the lattice arrangements and the filling rates, locally resonant PnCs (LRPnCs) are established for calculating sound insulation and bandgap characteristics. Furthermore, the nonuniform LRPnCs with Greek-cross chiral structure are constructed. To improve the sound insulation characteristics of the nonuniform chiral LRPnCs, a genetic algorithm (GA) optimization procedure is performed. Accordingly, the modified nonuniform chiral LRPnCs is designed and simulated to predict the sound insulation characteristics. Experimental verification suggests that the simulated results are in good agreement with the tested ones. The newly designed nonuniform chiral LRPnCs are effective in vehicle interior noise reduction. All the works are expected to be extended to other sound-related fields for noise reductions in engineering.

Active Vibration Control of Motor Driven Power Steering for Reduction of Interior Noise

This study presents a novel active vibration control (AVC) system on motor driven power steering (MDPS) to reduce interior noise reduction caused by operating the MDPS in an electric vehicle. MDPS is electronic power steering (EPS). The MDPS attached to the rack gear of power steering system is called R-MDPS. Operating of the R-MDPS generates a structural vibration of R-MDPS, and the vibration is transmitted to car body through mounts of car subframe. The vibrating body of car becomes a monopole and dipole sources of vibroacoustic noise generated inside car. This vibracoustic noise is a structure borne noise and makes passenger annoyance. To reduce interior noise inside a car directly, active noise control (ANC) has been used as active method and is a useful method for active cancellation of the low frequency noises less than 400Hz. However, in this study, because the frequency range of interior noise due to operation of R-MDPS is higher than 400Hz, the AVC system is employed and is applied to active cancellation of the vibration transmitted to car body through the subframe mounts. For application of AVC to test car, the control force is required and the actuator for generation of control force should be install on the mounts. For application of AVC to test car, the control force is required and the actuator for generation of control force should be inserted in the mount between subframe and R-MDPS. It requires an extra rework of test car. In this study to study the feasibility for the application of AVC system to R-MDPS, the test jig, which composes of R-MDPS and subframe of test car, is made and is set up in the laboratory. All study on AVC is performed in the laboratory. The proposed method is successfully applied to the active cancellation of vibration at target point of subframe. The developed method is going to be applied to the AVC of real test vehicle.

A Case Study Comparing Active Vs. Passive Enablers for Vehicle Interior Noise Reduction

The implementation of enablers on a luxury sport utility vehicle is used to illustrate the development process for reduction of road noise. The vehicle in this case study was launched into production with two tuned mass dampers for reduction of low frequency road noise content which was amplified by frame modes. Additionally, resonators were integrated into the wheels (rims) to address the dominant cavity resonance frequencies. The results of this successful production implementation are illustrated herein. An RNC (road noise cancellation) system was integrated into the case vehicle to assess its performance relative to the passive enablers listed above. This production representative (embedded software solution) RNC system utilized the vehicle's existing audio system for creation of active noise to cancel noise content which was predicted using accelerometers mounted to the vehicle chassis. A comparison of in-vehicle noise indicated a significant reduction at low frequencies (at all seating locations) when utilizing the active noise control solution. These noise improvements are coupled with a vehicle mass reduction of greater than 4 kg, when compared to the passive enabler solution.

Effect of Pavement Roughness on Arterial Noise Using Different Vehicle Types

For a healthy and sustainable environment, it is necessary to reduce the negative impact of noise on neighborhoods adjacent to arterials. The development of the automotive industry, the introduction of hybrid and electric vehicles, and improvements to vehicle bodies have made tire–pavement interaction the primary source of noise at regular traffic speeds. The objective of this study was to investigate the effect of pavement surface condition on noise levels for different vehicles, including gasoline, hybrid, electric vehicles, and a single-unit truck. Both interior and exterior noises were measured along rural and urban arterials. The exterior noise was measured using the controlled pass-by method. The results of the analysis indicated that pavement roughness and traffic speed had significantly influenced the interior noise level. It was found that the relationship between interior noise and vehicle speed, and pavement roughness is linear. Compared to gasoline car, hybrid and electric cars may reduce interior noise by 7 and 11 dB(A), respectively. For rural arterials and speeds of 80 km/h, exterior noise was strongly affected by pavement roughness. Analysis of exterior noise on urban arterials at 50 and 60 km/h speeds showed that pavement roughness has a significant impact on the noise level. In contrast, the noise analysis under two-speed levels, which are too close to each other, did not help in capturing the impact of speed on exterior noise. Therefore, further studies are recommended to highlight this issue. For a sustainable and healthy environment, it is vital to keep the pavement in good condition and increase the proportion of electric and hybrid cars in the vehicle fleet.

Study on interior noise control of minibus based on structural acoustic radiation

Aiming at the problem of excessive low-frequency noise inside a minibus, the interior noise control scheme was studied to improve the NVH (Noise, Vibration, and Harshness) performance of the vehicle based on the characteristics of the structural acoustic radiation. With acoustic contribution as the evaluation index, the ability of the structure to radiate noise to the vehicle was studied from the perspective of modal participation and panel contribution. In this study, the legacy finite element model of the vehicle was firstly established, and the model was validated through the modal test of the BIW (Body in White), and the noise transfer function analysis was carried out to identify the critical frequency points. Furthermore, the improved super element method (SEM) was used to establish the super element simulation model of the vehicle, the simulation analysis of the modal contribution and panel contribution was carried out for the critical frequency points, and the panels that provide the main contribution were determined. In addition, a single-factor experimental study was carried out on the position of the critical panel by using the dynamic vibration absorbers with different performance parameters, so as to verify the accuracy of the simulation results of the panel acoustic contribution for the critical frequency. Finally, the structural optimization schemes of the critical panels were designed and verified by experiments. It was indicated that optimizing the acoustic radiation characteristics of the structure by improving the body panel structure to reduce interior noise was feasible.

Coherence-based sensor set expansion for optimal sensor placement in active road noise control

Road noise is the dominant noise source that directly affects the vehicle noise, vibration, and harshness (NVH) performance. The active noise control (ANC) technology is a promising solution for reducing interior noise from tire–road interactions. Active road noise control (ARNC) systems include a set of acceleration sensors, which acquire vibrations that cause road noise, and the locations of the sensors is important to accurately determine the vibration transfer path. Therefore, it is necessary to find an optimal sensor set among the candidate sensors to maximize the performance of the ARNC system. The trial-and-error method for simulating all possible sensor combinations requires a high computational cost. This paper proposes a method that determines the set of reference sensor locations with the coherence analysis and the Fisher information matrix. The methodology starts with one sensor highly correlated with the output sound pressure level signals. The initial sensor set is iteratively expanded to the desired number of sensors by maximizing the determinant of the coherence information matrix. This approach can significantly reduce the amount of computation and subsequently shorten the time required. In addition, the obtained local optimal results indicated a reduction in broadband road noise of approximately 7 dBA and showed an error within 0.2 △dBA of the targeted noise reduction results in all driving conditions.

コヒーレントアウトプットパワーを用いた二輪車ヘルメット内部騒音の音源探査

Interior noise reduction is an important issue for motorcycle helmet quality. In this study, the relationship between the flow field outside the helmet and the internal noise was investigated for wind noise, and the aerodynamic sources that causes the internal noise were explored. Numerical simulation confirmed that the formation of vortices around the helmet. The acoustic field was generated at the point where the vortex convection caused by the detachment and reattachment of the flow, suggesting that the pressure fluctuation caused by the vortex formation contributed to the sound generation. Based on these numerical results, was experimentally measured using the coherent output power. As a result, strong correlations were confirmed among the shield, neck, and forehead/occipital projection areas. In particular, the shield and neck areas significantly contributed to the internal sound. The shield part is a stagnation point and the pressure fluctuation was small, suggesting the possibility of self-excited vibration with the hinge of the shield, while the neck part is thought to transmit internal sound due to pressure fluctuation caused by detachment and reattachment of the flow.

Study on accuracy improvement of predicting radiated sounds from interior panels using vibration speakers

Interior noises of railway vehicles especially on a high-speed railway are composed of a solid borne sound and a transmitted sound. It is necessary to take measures which consider the contribution ratio of radiated sound from each part in the interior of the car or the propagation path of these sound so as to reduce the interior noises efficiently. Moreover, the effect of reducing interior noise should be predicted before any measures are taken. In this study, we focused on predicting the interior noise with transfer functions and verified the proposed method proposed by conducting experiments using a high-speed railway test car and vibration speakers. In this paper, we made an attempt to improve the accuracy of noise prediction. First, we carried out shaking tests to estimate transfer functions using vibration speakers. On the basis of the acceleration of measuring points and the sound pressure of evaluation points on more interior panels than previously measured in the tests, the transfer functions were estimated. Secondly, we carried out the shaking test to simulate the acceleration of interior panels under the condition of train running. Finally, the interior noises were predicted by multiplying the acceleration obtained in the latter test by the transfer functions. As a result, the proposed method mostly predicted the interior noises and improved the accuracy of noise prediction.

Experiment and Evaluation Study on Rattle Noise in Automotive Seat System

With the reduction of vehicle interior noise, the Buzz, Squeak and Rattle (BSR) noises have become an intractable problem that needs to be tackled urgently. Seat system rattle noises have a large contribution to the passengers’ complaints, due to the close distance between the passengers and seats. The seat structure and its components can be sources of rattle noise based on their physical characteristics. The aim of the present paper is to characterize the sound quality property of rattle noise in seat system, and subsequently, use the characteristics of the rattle noises to assess the subjective responses to the noise. In this study, sound metrics are computed for the signals recorded at different points in the seat system. To be more specific, the signals are recorded before and after the durability test in different loading states. Consequently, the characteristics of the rattle noises were compared and analyzed, and the jury test was performed. On this basis, a rattle index and evaluation models were developed. It is expected that the developed rattle evaluation system and sound quality index can be used to reduce the automotive interior rattle noise in terms of subjective levels as well as objective levels.

차륜형장갑차 실내용 흡음재 성능개선 및 엔진 인캡슐레이션을 통한 주행 실내소음 개선 연구

차륜형장갑차 실내용 흡음재 성능개선 및 엔진 인캡슐레이션을 통한 주행 실내소음 개선 연구

Localization of Increased Noise at Operating Speed of a Passenger Wagon

Noise generated by railway wagons in operation is produced by large numbers of noise sources. Although the railway transport is considered to be environmental friendly, especially in production of CO2 emissions, noise is one of problems that should be solved to keep the railway transport competitive and sustainable in future. In the EU, there is a strong permanent legislation pressure on interior and exterior noise reduction in railway transport. In the last years in Slovakia, besides modernization of existing passenger wagons fleet as a cheaper option of transport quality improvement, quite a number of coaches have been newly manufactured, too. The new design is usually aimed at increased speed, higher travel comfort, in which reduction of noise levels is expected. However, not always the new designs meet all expectations. Noise generation and propagation is a complex system and should be treated such from the beginning. There are possibilities to simulate the structural natural frequencies to predict vibrations and sound generated by these vibrations. However, the real picture about sound fields can be obtained only by practical measurements. Simulations of the wagon’s natural frequencies and mode shapes and measurements in real operation using a digital acoustic camera Soundcam have been done, which showed that for the calculated speeds the largest share of noise from the chassis was not radiated through the floor of the wagon, as was expected, but through the ceiling of the wagon. To improve the acoustic properties of the wagon at higher speed, it was proposed to use high-volume textile insulation in the ceiling of the wagon. The paper briefly presents modern research approaches in the search for ways to reduce internal noise in selected wagons used in normal operation on the Slovak railways.

Active Sidewall Panels with Virtual Microphones for Aircraft Interior Noise Reduction

This work deals with the reduction of aircraft interior noise using active sidewall panels (linings). Research work done in the past showed that considerable reductions of the sound pressure level (SPL) in the cabin are possible using structural actuators mounted on the lining and error microphones distributed in front of the linings. However, microphones are undesirable for error sensing because they are not suitable for the realisation of an integrated and autonomous active lining (smart lining module). Therefore, the goal of the present work is the replacement of the microphones by structural sensors. Using the structural sensors as remote sensors in combination with an acoustic filter, virtual microphones can be defined. The present study relies on experimental data of a double-walled fuselage system which is mounted in a sound transmission loss facility. Simulation results based on measured time data and identified frequency response functions are provided. Different configurations of virtual microphones are investigated regarding the SPL reduction and the induced vibration of the lining panel.