Pass-by Noise Research Articles

Application of acoustic metamaterial for tire noise reduction

Increased traffic volume leads to increased noise emitted by the vehicles. Additionally, the lightweight design of vehicles worsens the noise, vibrations and harshness behavior. The total noise of the vehicle consist of multiple sources. We focus on the influence of sound emitted by the tire on the interior cabin noise and on the pass-by noise. To address the problem, we develop two different wheelhouse liners based on a compound material and an acoustic metamaterial, respectively. The compound material consists of porous layers as well as a microperforated panel. The acoustic metamaterial relies on a periodic arrangement of local resonators. Both materials are numerically modeled and experimentally validated. We first measure the absorption coefficient of the liner in the Alpha Cabin. We then mount the liner to a vehicle and subsequently measure the performance of the full vehicle. We achieve improved performance in terms of sound attenuation and thus are able to reduce both, the cabin noise and the pass-by noise, significantly.

Rail noise across three states in Australia—Operational noise assessment on Inland Rail

Inland Rail Project is a proposed 1700 km freight rail line connecting Melbourne and Brisbane via three States in Australia–Victoria, New South Wales, and Queensland. Operational rail noise assessment is undertaken differently across these States in Australia. The assessment generally considers the existing and future noise exposure across day and night, along with single pass-by maximum levels. However, the assessment durations and statistical means of assessing single events differ across the States. The key acoustic criteria relevant to operational noise assessments and how they differ across the project footprint are discussed in this paper. Specifically, the effect of application of various criteria in the project context are discussed, along with statistical analysis of train pass-by noise data sets. A Monte-Carlo based methodology is proposed for estimating Single Event Maximum, a criterion for assessing single rail-noise events in Queensland. The methodology is discussed in the context of field data and greenfield scenarios where the method may be beneficial for acoustic consultants. The effects of inclusion of noise sources such as train horns and crossing bells are also briefly discussed. Finally, a proposed methodology for a consistent assessment of rail noise on such nationally spread projects is discussed.

A Fast Approach to Optimize Tread Pattern Shape for Tire Noise Reduction

Impact force induced by tread pattern is one of the major mechanisms of tire noise; thus, how to reduce tire impact noise has been an important issue in regard to tire technology. In this paper, the mechanism of tire–pavement interaction noise is briefly described, and a prediction model for pattern noise is proposed. The prediction model was validated with indoor semi-anechoic chamber and pass-by noise experiments. Then, an optimization method for the tread pattern was proposed by using the basis vector method, and the synthetic pattern shape was generated through a linear combination of basis shape vectors. Finally, a novel multi-objective function was proposed, aimed at minimizing the impact noise generated by the tire pattern, and the weight factors of the basis vectors were optimized with a genetic algorithm. The method proposed in this paper can be used to evaluate or improve pattern performance and reduce trial and error in the pattern design stage.

Influence of the Doppler effect and binaural characteristics on perceived annoyance of train pass-by noise

High-speed train has advantages on large seating accommodation among green transportation systems. Commercial trains continuously increase its operation speed to reduce the travel time. The noise generated from railway operation prevents nearby residential areas from quiescent and comfortable living space. When evaluating the noise annoyance caused by high-speed train operations, it is necessary to consider the acoustic characteristics as well as its magnitude. In particular, the pass-by noise has a rapid frequency shift due to the Doppler effect of moving noise source. In this study, a simple wave field model is proposed to reflect the Doppler effect and binaural characteristics. The noise emitted from an operating high-speed train (KTX) was measured, and the spectral characteristics were analyzed. The frequency shifts due to the Doppler effect were observed. The rolling and aerodynamic noise generated from the inter-coach space contributed to the pass-by noise. To investigate the effects of the Doppler effect, the moving sounds were synthesized with the frequency shift at the corresponding bands. The synthesized sounds were convolved with a simple head-related transfer function to represent the binaural characteristics. The pairwise comparison method was used for auditory annoyance evaluation of the synthesized moving sound stimuli and quantification of the Doppler effect. It was determined that the Doppler frequency shift reduced annoyance of the moving sound source. This reduction appeared only when binaural effects were considered together with the frequency shift. The identified influence of the Doppler effect helps to understand the railway noise bonus compared to those from other transportation systems.

On the efficient simulation of pass-by noise signals from railway wheels

The article presents an approach for calculating pass-by sound pressure radiated from railway wheels in the time domain using moving Green’s functions. The Green’s functions are obtained by using Finite Element (FE) and Boundary Element (BE) methods in the frequency domain, subsequent inverse Fourier transform, followed by convolution with a time series of rolling contact forces to obtain the pass-by time signals. However, traditional BE methods are computationally expensive due to the low structural damping of the wheel, necessitating a high frequency resolution.To overcome this issue, a modal approach is introduced in which the pass-by sound radiated by each wheel mode is calculated separately. This approach incorporates the dynamic response of the wheel in the time-domain processing and thus reduces the cost of the BE solution. A modal source signal is introduced to describe the excitation of each mode at each time step. The sound field radiated by unit modal amplitudes is calculated in BE and subsequently approximated by spherical harmonic (SH) equivalent sources, which allows for efficiently calculating acoustic transfer functions for varying relative positions of the wheel and a stationary receiver. Convolution of the source signal with the moving acoustic transfer function produces the pass-by pressure signal.The article investigates the directivity of the radiation from each mode and finds that most modes, including those with dominant radial deflection, radiate in mostly axial direction at high frequencies. Modes that dominate the pass-by pressure level are identified, both in frequency bands and with respect to the relative positioning of the wheel to the receiver. Finally, it is found that an SH expansion order of approximately 30 is required to satisfy the employed error measures, although lower orders may suffice for an auralisation of the signal.

Source contribution analysis of vehicle pass-by noise using a moving multi-band model based OPAX method

The conventional operational path analysis with eXogeneous inputs (OPAX) method has been widely used to investigate the vibration transfer paths. However, the single degree of freedom model is not available for the load identification of acoustic sources due to their unknown source behavior. And the alternative multi-band (MB) model can only offer a deterministic estimation to the load parameters. To assess the acoustic source contribution of vehicle pass-by noise (PBN), this paper develops the OPAX method by introducing a moving multi-band model (MMB). In this method, the vehicle acoustic sources are simplified as a combination of a series of point sources. The source loads are firstly parametrically modelled by MB models. Then the load parameters are solved several times in the MMB and estimated by the index of coefficient of variation, which suppresses the effect of nonlinear random noise and improves the load identification accuracy of acoustic sources. Finally, the source contributions to PBN at receivers can be derived. Both numerical studies and experimental validations are implemented to examine the performance of the proposed method. Results show that compared to the conventional OPAX method, the proposed method can provide a higher accuracy for the source contribution analysis of PBN.

Development, Construction and Certification of a Facility for Exterior Noise Regulatory Compliance Testing

OEMs are required to meet applicable regulations for exterior noise. Acceleration noise (typically called pass-by noise) regulations have an upper limit for noise emission. In addition, vehicles which can operate without a combustion engine must comply with regulations for minimum noise emitted during low speed driving. In order to make regulation-compliant measurements for global destinations, a test track meeting requirements of ISO 10844 may be necessary. However, strictly meeting this requirement doesn't guarantee a usable facility for efficient measurements. This paper describes design goals, challenges and construction of a regulation compliant facility in Arizona. The intent was to build a facility with a long usable life before requiring repaving, sufficient isolation from nearby test roads, 24-hour usability and onsite amenities to accommodate technical staffs and vehicle retrofits. Consideration of needs of all stakeholders was necessary to make a facility not only regulation-compliant but also attractive to internal and external customers.

Light rail wheel/rail noise radiation model using a coupled FE-BE method

This paper presents the development of a coupled finite element - boundary element model of rolling noise from a resilient light rail wheel on several types of tracks. The vibro-acoustic model utilizes a 3D elastic solid representation for both wheel and rail which are excited by linearized Hertzian interface loads. Estimates of the radiated sound power, radiation efficiencies and wayside noise levels are obtained and then scaled using a parallel impedance framework and a roughness profile. Results are compared to recently measured vehicle passby noise and track decay rates at Sound Transit in Seattle Washington.

Recent advances on research into high-speed railway noise

Abstract Around 42,000 km high-speed railways are in operation in China with a maximum speed of 350 km/h. Trains which can run at 400 km/h are also under development. To control both train pass-by and train interior noise, huge resources have been put into research on high-speed railway noise, and the authors of this paper and their teams have been involved in several key projects. This paper is to summarise some of the advances achieved in these projects by covering the following topics: measurement results and characteristics of high-speed railway pass-by noise; analyses on source contribution to pass-by noise based on microphone array measurement; modelling of high-speed rolling, aerodynamic, and viaduct bridge noise; prediction of the vibro-acoustic behaviour of car-body with poro-elastic media; analyses of vibration transmission in the suspension/bogie system; statistical energy analysis-based prediction of train interior noise. Open problems and potential technologies for controlling high-speed railway noise are also discussed.

Predicting vehicle category using psychoacoustic indicators from road traffic pass-by noise

A set of road traffic pass-by noises containing more than 2000 vehicles was recorded following the Statistical Pass-By (SPB) methodology (ISO 11819-1:2022). Besides the acoustic descriptors, psychoacoustic indicators (loudness, sharpness, roughness, fluctuation strength) were retrieved for each pass-by of the three vehicle categories defined in the standard (passenger cars, dual-axles and multi-axles heavy vehicles). A fourth vehicle category, comprised of delivery vans, was also investigated. All psychoacoustic indicators significantly differed among vehicle categories, meaning that not only intensity descriptors but also temporal and spectral features of pass-by noise distinguish those classes. With enough instances and a balanced dataset across groups, a machine-learning classification algorithm was trained with 70% of the dataset to predict vehicle categories using the psychoacoustic indicators. Classification accuracy on the test set reached 72.5%. Accuracy losses were primarily caused by 25% of the actual passenger cars being misclassified as vans and vice-versa. Pooling these two categories increased accuracy to 82%. With more descriptors from road traffic pass-by noise than uniquely its maximum noise level, limiting definitions of vehicle categories may be overcome. As a result, measurements such as the SPB can become broader and vehicle fleets worldwide more consistently represented in terms of noise perception.

Noise Emission Models of Electric Vehicles Considering Speed, Acceleration, and Motion State.

Electric vehicles, known for their low-noise emission, are popular and widespread in metropolises in China, and they provide an opportunity for a reduction in environmental noise from vehicles. To understand the noise from electric vehicles better, this study develops noise emission models considering speed, acceleration, and motion state. The model construction is based on the data collected from a pass-by noise measurement experiment in Guangzhou, China. The models describe a linear relationship between the noise level, the logarithm of speed, and the acceleration for multiple motion states (i.e., the constant-speed state, the acceleration state, and the deceleration state). From the spectrum analysis, the low-frequency noise is barely affected by the speed and acceleration, but the noise at a certain frequency is most sensitive to them. Compared to other models, the proposed ones have the highest accuracy and the greatest ability for extrapolation and generalization.

Vehicle pass-by noise auralization in a virtual urban environment

Auralization is a suitable method for the subjective evaluation of environmental noise. Due to its complexity, the plausible and immersive acoustic representation of outdoor scenarios in urban environments is an ongoing field of research. This work presents the design and implementation of a vehicle pass-by noise model with application in a real-time environmental noise auralization. The pass-by noise sources are implemented by procedural audio syntheses of engine and road-tyre noise with according directivities. In an audiovisual demonstration, the resulting source model is auralized considering the sound propagation phenomena in a virtual urban environment using the Virtual Acoustics framework.

Implementation of measurement uncertainties into vehicle noise regulation

The current vehicle noise regulation UN R51.03, does not provide specific considerations for the measurement uncertainties related to the measuring method for external pass-by noise. The measurement method is based on the ISO Standard ISO 362-1:2007. While the ISO system mandates a detailed description of the expected uncertainties, the UN-ECE has not overtaken these uncertainty considerations, as the application of the test method is limited to type-approval and conformity of production measurements, both under control of the vehicle manufacturer in agreement with a type- approval authority. The UN ECE Working Party on Noise and Tyres (GRBP) in Geneva established in 2019 an Informal Working Group on Measurement Uncertainties (IWG MU), to evaluate the measurement uncertainty in general and to propose amendments to regulations to reduce the measurement uncertainty, starting with the most important sound emission regulations UN R51.03 (vehicles) and UN R117.02 (tyres). This paper describes the principal work of the IWG concerning the contribution of the different parameters to the overall expanded uncertainties when testing vehicles according to the specifications in UN R51.03. The identified main contributors to the overall measurement uncertainties are variations due to the test track (site-to-site) and air temperature effects (day-to-day).

Quantifying the annoyance caused by flat tops on the wheels of railway vehicles

As part of a research project by the Federal Environment Agency measurements of the pass-by noise of railway vehicles with and without flat spots on the wheels were conducted. The aim of the project was to define an acoustic maintenance criterion for the wheels. To do so listening tests were carried out to quantify the annoyance the noise caused by a flat spot. In order to determine the level adjustment equivalent to the increased annoyance caused by the flat spot, the following method of adjustment was used. The test subjects were each presented a pair of sounds consisting of a vehicle passing with and a vehicle passing without a flat spot. By raising or lowering the level of the signal without a flat spot, the test subjects were able to adjust the two signals individually to "equal annoyance". Furthermore different noise levels and psychoacoustic indices were tested in order to describe the impact of the flat spot on the caused annoyance.

Unsteady FW-H Simulation of the Aerodynamic Noise of a High Speed Train Bogie

Aerodynamic noise is generated by interaction of the air flow with an object and within the turbulent flow itself. In railways it becomes an important noise source for speeds above 250 kph and major areas of noise generation on trains, in particular high speed trains, are the train head, the leading and second bogie, the pantograph and the gaps between trailers. In this presentation a numerical simulation approach based on CFD/CAA techniques aiming to predict aerodynamic noise of different components of SNCF's TGV high speed trains. The approach is based on an unsteady DES flow simulation combined with the Ffowcs-Williams and Hawkins (FW-H) analogy for the acoustic part. In order to develop the method different models are implemented and the leading bogie was selected as an application case. A simplified symmetric model will be compared against a full, higher resolved model in order to see if computation time gains are feasible. Results of this simulation, in terms of sound power and directivity, are already used by SNCF noise experts in order to estimate pass-by noise levels of TGV high speed trains. Furthermore, noise mitigation solutions can be tested virtually with the suggested approach before being tested with a prototype.

Psychoacoustic Analysis of Various Train Pass-by Noise Using

Due to the recent high speed of railway, noise and vibration generated during operation has emerged as a major social problem. Specially, the internal noise of railway varies depending on various operating conditions such as speed, vehicle crossings, and tunnel entry, and has a great effect on the riding comfort of passengers. In this study, an evaluation method for binaural noise of train pass-by noise and a simple wave field model which can reflect the Doppler effect are examined. To reflect the binaural characteristics of train pass-by noise, binaural measurements were conducted for several types of train, different measurement distances and various measurement angles. The annoyances of measured binaural noises were analyzed using conventional sound pressure level, psychoacoustic metrics, and their rate of change. Also, the noise emitted from high-speed railways was measured and characterized. By its analysis result, moving sounds were synthesized considering an initial frequency and a frequency shift. The synthesized sounds were convolved to reflect binaural condition. Auditory experiments were conducted using the synthesized moving sound stimuli, and the effects of the Doppler frequency shift on annoyance of moving sound sources were obtained.

Auralisation of combined mitigation measures in railway pass-by noise

To reduce noise exposure along railway lines various combinations of noise mitigation measures can be considered. However, predicting and assessing their effects is non-trivial and the potential need for multiple measures is difficult to communicate to stakeholders. Auralisation is a promising tool that can help to support communication and decision-making, and enable psychoacoustic evaluations. This paper presents developments of a physics-based auralisation model for train pass-bys that allows various mitigation measures to be included. The work is conducted within the European research project SILVARSTAR. The proposed model includes contribution from rolling noise, impact noise, traction, auxiliary systems, and aerodynamic noise. It is physically based and allows a direct assessment of pass-by parameters such as speed, roughness, wheel flats and track design. Based on the TWINS model, five structural transfer paths for rolling noise are considered to integrate mitigation measures such as wheel and rail dampers. Shielding by noise barriers is simulated with analytical models. Reflection at different ground types is considered and can account for track embankments. The results can be coupled to an immersive Virtual Reality environment, by first panning the synthesised sounds to a small virtual speaker array and subsequently dynamic binaural rendering for headphones.

Hydre: a noise radar to automatically track down excessively noisy vehicles in real traffic conditions

The developments made by Bruitparif since 2016 around sound source localization technologies applicable to the field of environmental noise resulted in the launch on the market of a patented combined acoustic and imaging sensor called "Medusa". An article of law was voted in France at the end of 2019 in order to enable the experimentation of noise radars in order to punish drivers causing significant noise nuisances by their behavior. The evaluation process includes track trials, roadsite tests and a final phase with fines. We will describe this national experimentation and the context in which it takes place. We will then detail the prototype called "Hydre" that we have developed for this purpose, and will present case results showing how it solves the major difficulties of the legal measurement of the pass-by noise of vehicles in real traffic conditions.

Classification of noisy vehicles from unsupervised measurements

The NEMO-project (https://nemo-cities.eu/) aims to identify noisy and polluting road and rail vehicles, using remote sensing technology. Noise levels from individual road vehicles are measured from the roadside, in normal traffic. Road authorities may use these data to enforce noise limits, to limit access to Low Emission Zones or to influence driving behaviour. Whether a vehicle is a 'high noise emitter' is a complex question, as the noise level depends on vehicle type and condition, driving style, weather and location-specific characteristics. From a legal perspective, the question may be answered in relation to type approval noise limits, or in relation to local noise disturbance regulations. Within NEMO, a classification model is developed from a large dataset of unsupervised pass-by noise measurements, from different locations. The model labels noisy vehicles based on the noise measurements, technical vehicle data, driving conditions, and external factors. Several modeling and machine learning techniques were evaluated, to find the most accurate solution. This paper presents the results, and it looks forward to how the technological solution could be applied to enforce regulations, leading to a reduction of traffic noise annoyance.

Real-time sound synthesis of pass-by noise: comparison of spherical harmonics and time-varying filters

This paper proposes and compares two sound synthesis techniques to render a moving source for a fixed receiver position based on indoor pass-by noise measurements. The approaches are based on the time-varying infinite impulse response (IIR) filtering and spherical harmonics (SH) representation. The central contribution of the work is a framework for realistic moving source sound synthesis based on transfer functions measured using static far-field microphone arrays. While the SHs require a circular microphone array and a free-field propagation (delay, geometric spread), the IIR filtering relies on far-field microphones that correspond to the propagation path of the moving source. Both frameworks aim to provide accurate sound pressure levels in the far-field that comply with standards. Moreover, the frameworks can be extended to additional sources and filters (e.g. sound barriers) to create different moving source scenarios by removing the room size constraint. The results of the two sound synthesis approaches are preliminary evaluated and compared on a vehicle pass-by noise dataset and it is shown that both approaches are capable of accurately and efficiently synthesize a moving source.