Vehicle Pass-by Noise Research Articles

Impedance measurements on reflective surfaces: effect of nodes

The ISO 13472-2 standardizes the in-situ measurement of normal-incidence acoustic absorption of road pavements. The standard describes the use of the two-microphone method with an impedance tube specially configured for sealing against pavement surfaces. The method is of interest to the tire-pavement noise and vehicle pass-by noise communities. For roads constructed of dense graded asphalt, for example, pass-by noise test tracks conforming to ISO 10844, the pavement is a highly reflective surface. Under this measurement condition, the acoustic field within the tube develops nodes at one or the other microphone positions at characteristic frequencies. These nodes present as sharp peaks and valleys in the two-microphone transfer function. Such narrow bandwidth features are susceptible to measurement error, in particular, signal processing leakage as evidenced by significant drops in the coherence function at the frequencies of the nodes. In this paper we study the nature of the nodes and the effect they have on the two-microphone transfer function and coherence function. We further investigate how different formulations of the transfer function affect the overall 1/3rd octave band accuracy. The effect of the number of averages on both coherence and leakage error is assessed. The potential to solve this leakage effect by switching microphones to other positions is evaluated in relation to a procedure with two fixed microphones. It was concluded that although shifting microphone positions does have advantages in terms of preventing leakage, the mandatory application of a reference measurement reduces the overall error. Finally, recommendations for improving the procedure in ISO 13472-2 are formulated.

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.

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.

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.

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.

A Vehicle Pass-by Noise Prediction Method Using Ray Tracing with Diffraction to Extend Simulation Capabilities to High Frequencies

<div class="section abstract"><div class="htmlview paragraph">Predicting Vehicle Pass-by noise using simulation enables efficient development of adequate countermeasures to meet legislative targets while reducing development time and the number of physical trial-and-error prototypes and tests. It has already been shown that deterministic simulation methods such as the Boundary Element Method (BEM), which may also include directivity of sources, can support the trim package optimization process for Pass-by noise, especially for low to mid frequencies. At higher frequencies, the Ray Tracing technique, can represent an efficient alternate providing options to trade off speed versus accuracy compared to wave-based technique such as FE/BEM. This paper presents a Ray Tracing approach with high order diffraction effect. Moreover, source directivity and sound package effect are accounted for. Validation examples for predicting Pass-by noise which complements other deterministic methods and extends practical prediction capabilities to higher frequencies are presented.</div></div>

Accurate and controled vehicle pass-by noise emission quantification in real life traffic

Noise emission from individual vehicle largely contributes to city pollution and has serious health impact. The standards towards vehicle manufactures consists in pass-by testing with specific acceleration conditions which are not representative of all real driving. For the 2015/996 EU directive, the vehicle source model is inspired of the preceding pass-by standard with derived data represented the propulsion and rolling noise sources. Anyhow, those sources are underestimated due to driving behavior, aged and modified vehicle, road surface, meteorological conditions... The true data collection of vehicle pass-by would be interesting. Moreover, some of the countries are reflecting on how to fight against those extremely noisy vehicle exceeding noise limit with efficient monitoring systems. This paper presents an innovative tool able to detect, identify and quantify the noise emission of individual pass-by vehicle in real life traffic. It is based on the combination of array and video processing. Compared to the state of the art and thanks to MEMs technology, the system is optimized and designed to quantify the individual noise vehicle emission regarding standard with controlled measurement and accurate processing. If the conditions are not respected to properly qualify the pass-by regarding the system limits, the data are ignored. It aims at constructing large and accurate database useful to determine average noise levels and/or acceptable noise limits per vehicle category.

Short-term noise annoyance and electrodermal response as a function of sound-pressure level, cognitive task load, and noise sensitivity.

Introduction:Two aspects of noise annoyance were addressed in the present laboratory study: (1) the disturbance produced by vehicle pass-by noise while engaging in a challenging non-auditory task, and (2) the evaluative response elicited by the same sounds while imagining to relax at home in the absence of a primary activity.Methods and Material:In Experiment 1, N = 29 participants were exposed to short (3-6 s) pass-by recordings presented at graded levels between 50 and 70 dB(A). Concurrent with each sound presentation, they performed a visual multiple-object tracking task, and subsequently rated the annoyance of the sounds on a VAS scale. In Experiment 2, N = 30 participants judged the sounds while imagining to relax, without such a cognitive task.Results and Discussion:Annoyance was reduced when participants were engaged in the cognitively demanding task, in Experiment 1. Furthermore, when occupied with the task, annoyance slightly, but significantly increased with task load. Across both experiments, the magnitude of simultaneously recorded skin conductance responses in the first 1-4 s after the onset of stimulation increased significantly with sound pressure level. Annoyance ratings tended to be elevated across all sound levels, though significantly only in Experiment 2, in participants classified as noise sensitive based on a 52-item questionnaire.Conclusions:The results suggest that noise annoyance depends on the primary activity the listener is engaged in. They demonstrate that phasic skin conductance responses may serve as an objective correlate of the degree of annoyance experienced. Finally, noise sensitivity is once more shown to augment annoyance ratings in an additive fashion.

Effect of temperature on road pass-by noise of light vehicle

Traffic noise is an important evaluation index of urban environmental quality. The level of traffic noise is affected by many environmental factors. Compared with close proximity method (CPX method) in measurement for calculating temperature coefficient, using statistical pass-by method (SPB method) is more suitable for traffic noise evaluation. In order to verify the influence of temperature on road traffic noise, we use SPB method and light vehicles to track and test different types of road noise in a period of time, and record the road temperature and air temperature at the same time. The experimental results show that the vehicle pass-by noise decreases with the increase of temperature, and the noise level of porous asphalt pavement changes little with temperature compared to dense graded pavement.

Sensitivity analysis and propagation of uncertainty for the simulation of vehicle pass-by noise

The study presented in this paper aims at developing an aid to the modeling of the pass-by noise of a vehicle, as called for in regulatory testing. The goal is to accurately predict and evaluate noise emissions earlier in the vehicle development cycle, i.e. before the industrialization stage. For these reasons, a synthesis model is developed. This model combines the acoustic flow of the most influent sources (powertrain, intake, exhaust tail, exhaust line, tire/road noise), with the acoustic transfer between these sources and the microphone located at 7.5 m from the axis of the test track, taking into consideration the motion of the vehicle. The input parameters of these models are considered uncertain; therefore, an uncertainty quantification study is first performed. These uncertainties are then propagated in these models using quasi-Monte Carlo methods. Finally, a sensitivity analysis study is carried out to study the impact of the variability of the input parameters on the variability of the output noise levels of the synthesis models. Influential parameters have been identified and classified by vehicle family.

A Fast Method of Feature Extraction for Lowering Vehicle Pass-By Noise Based on Nonnegative Tucker3 Decomposition

Abstract Usually, the judgement of one type fault of vehicle pass-by noise is difficult for engineers, especially when some significant features are disturbed by other interference noise, such as the squealing noise is almost simultaneous with the whistle in the exhaust system. In order to cope with this problem, a new method, with the antinoise ability of the algorithm on the condition by which the features are entangled, is developed to extract clear features for the fault analysis. In the proposed method, the nonnegative Tucker3 decomposition (NTD) with fast updating algorithm, signed as NTD_FUP, can find out the natural frequency of the parts/components from the exhaust system. Not only does the NTD_FUP extract clear features from the confused noise, but also it is superior to the traditional methods in practice. Then, an aluminium-foil alloy material, which is used for the heat shield for its lower noise radiation, replaces the aluminium alloy alone. Extensive experiments show that the sound pressure level of the vehicle pass-by noise is reduced 0.9 dB(A) by the improved heat shield, which is also considered as a more lightweight design for the exhaust system of an automobile.

Blind Source Separation Applied to Indoor Vehicle Pass-By Measurements

Indoor vehicle pass-by noise applications deal with measuring the exterior noise from a vehicle fixed on a chassis dynamometer in a large hemi-anechoic room. During a standardised acceleration test, the noise is measured with an array of microphones placed in the far-field, and the overall noise level versus vehicle position can be simulated. The indoor facility allows controlled and repeatable measurements independent of weather. For engineering purposes, pass-by contribution analysis can be included in the test leading to information about the pass-by noise contribution from major noise sources. This work presents a novel application of blind source separation to vehicle measurements from an indoor pass-by measurement campaign. In contrast to the classical transfer path approach using point sources for modelling vehicle noise sources and combining an operational measurement with transfer functions, the blind approach does not consider a specific noise source model. It only assumes that the noise is produces by a set of independent noise sources using only a single operational measurement for a given vehicle condition as input. Near-field microphone measurements are blindly separated into independent components and further correlated with the signals measured at the far-field indoor pass-by microphones to get the time-domain contributions. Finally, we apply the indoor simulated pass-by algorithm to produce noise contribution levels as a function of vehicle position. We discuss the specified application of blind source separation to vehicle measurements for different operating conditions from a real indoor pass-by test. Separation of tyre and engine related noise at tyre near-field microphones is verified. Furthermore, the tyre pass-by noise contribution is extracted from the overall vehicle measurement.

Decomposition and visualization of vehicle noise sources with transfer path acoustical holography

Decomposition of noise sources is an essential step to reduce the vehicle pass-by noise. Dynamic transfer path analysis has been used to describe the relation between the noise sources of the vehicle and the response point in the pass-by test. A transfer path acoustical holography method is introduced to decompose and visualize the vehicle pass-by noise sources, and the method is illustrated with a simulation of four moving point sources. The decomposition results for the four sources using transfer path acoustical holography are compared with that using acoustical holography method. It shows that the transfer path acoustical holography method has a better decomposition result. Finally, the proposed method is used to decompose the contributions of the sources in a commercial truck. The results show that the transfer path acoustical holography can be used to decompose and visualize the vehicle's noise sources in the pass-by test.

S0505-2-5 道路交通騒音の常時監視に向けた複合型音源定位法(車両・機体・流体機械に関連した騒音問題へのアプローチと対策(2))

We aim to develop a noise source localization apparatus to detect the noisy vehicle from road traffic noise. This apparatus is consisted of microphone array, camera and processing computer. The microphone array is set upside of running vehicles. Now various types of vehicle pass-by noise exist in traffic flow. Therefore traffic noise is broadband acoustic noise. Hence, wide frequency range is required for source localization method. Though, present methods can't cover such a wide frequency range by itself When we try to locate traffic noise source by present method, it is required too big microphone array to install on the street. This paper proposes a technique that is a hybrid of the beamforming method and the sound intensity method. In order to study the effectiveness of this technique, we performed a test using actual vehicles driven on the test grounds.

Estimation of Vehicle Pass-By Noise Emission Levels from Onboard Sound Intensity Levels of Tire–Pavement Noise

As a portion of the overall research work for NCHRP Project 1-44, field tests were performed on in-service pavements to demonstrate the applicability of the onboard sound intensity (OBSI) method for quantifying the effect of different pavement types in relation to total vehicle noise emissions measured with the controlled pass-by (CPB) and statistical pass-by (SPB) methods. Testing included the simultaneous measurement of OBSI on two specific candidate test tires, CPB on test vehicles equipped with those tires, and SPB of both light and heavy-duty vehicles. With the SPB data, the relationship between OBSI tire–pavement noise and average vehicle noise emissions were examined for both light vehicles and heavy trucks. To account for site-to-site variation, pass-by results were normalized by using the measured relationships between OBSI and CPB levels for each site. On the basis of these results, it was found that SPB levels for both light vehicles and heavy trucks could be predicted accurately with a standard deviation of 0.8 dB for both vehicle categories for an average of sites that used OBSI data obtained from either of two candidate light-vehicle test tires.

Analysis and optimisation of vehicle pass-by noise

In order to allow an efficient analysis and optimisation of the pass-by noise of vehicles, a new software tool has been developed to analyse the contribution of all single noise sources to total pass-by noise with high accuracy in a very short time. This article by AVL List GmbH, Graz, Austria, describes the theoretical approach, the establishment and the verification of the methodology and the main features of the pass-by noise analysis software tool.

Using Multi-Layer Perceptrons to Predict Vehicle Pass-By Noise

All new vehicle designs have to pass a legislative, noise emission test – the ‘pass-by noise’ test. In the highly competitive automotive industry, it is important to predict the test result early in the design process, rather than waiting until a prototype is built. Engineers can ‘guess’ test results about aswell as the best, although inadequate, analytical models. They achieve this by using experience and their knowledge of acoustics and of the vehicle’s design. Neural networks should also be capable of pass-by noise prediction, learning from the results of previous tests. This paper describes a neural network approach to the problem. First, expert knowledge is used to select vehicle design and test parameters to present as inputs to a multi-layer perceptron. Since data is scarce, the problem is broken down into two stages, vehicle performance and pass-by noise. The two trained networks are evaluated and their performance discussed.

Simulation of Vehicle Pass-by Noise Radiation

This paper presents an extended Kirchhoff integral formulation for predicting sound radiation from an arbitrarily shaped vibrating structure moving along an infinite baffle. In deriving this formulation, the effect of sound reflection from the baffle is taken into account by using the image source theory. Moreover, the effect of source convection motion and that of motion-induced fluid-structure interaction at the interface on the resulting acoustic pressure field are considered. The formulation thus derived is used to calculate sound radiation from a simplified vehicle model cruising along a solid ground at constant speeds. Since analytical and benchmark numerical solutions for an arbitrarily shaped vibrating object in motion are not available, validations of numerical results are made with respect to those of a point source. Next, sound radiation from a full-size vehicle is simulated. For simplicity, the vehicle is assumed to be made of a shell-type structure and excited by harmonic forces acting on its four tires. Vibration responses subject to these excitations are calculated using finite element method (FEM) with HyperMesh® version 2.0 as pre- and post-processors. Once the normal component of the surface velocity is specified, the radiated acoustic pressure fields are determined using boundary element method (BEM). Numerical results show that the effect of source convection motion enhances sound radiation in the forward direction, but reduces that in the rearward direction. Changes in the resulting sound pressure fields become obvious when the Mach number exceeds 0.1, or equivalently, when a vehicle cruises at 70 mph or higher.

Perception of the Vehicle Pass-by Noise on Different Road Surfaces

Perception of the Vehicle Pass-by Noise on Different Road Surfaces

Assessment of tire/pavement interaction noise under vehicle passby test conditions using sound intensity measurement methods

Over the past several years, sound intensity measurement methods have become an increasing valuable tool in isolating tire/pavement interaction noise when a vehicle is tested under full throttle acceleration conditions such as the ISO 362 R15 procedure. Several investigations have been conducted and reported which demonstrate the relationship between ‘‘on-board’’ sound intensity measured close to a tire contact patch and the sound pressure level measured by a stationary microphone 7.5 m away from the line of travel of the vehicle. Using these relationships, the contribution of tire/pavement noise can be assessed relative to other noise sources associated with a vehicle under acceleration as measured at 7.5 m. In this application, it has been determined that some tires can produce significantly higher noise levels under the torque of acceleration than under cruise conditions. Sound intensity has also been used to separate sound propagation from sound generation effects in the assessment of test surfaces such as those specified by SAE and ISO. This paper reviews the various applications of sound intensity in the assessment of tire/pavement interaction noise issues related to vehicle passby noise, the implication of recent findings on noise reduction strategies, and the potential for standardization of sound intensity techniques.