Pass-by Noise Research Articles

A study on aerodynamic pass-by noise based on equivalent source method

Pass-by noise generated by high-speed trains is an important influencing factor on the surrounding environment and is getting more and more attention with the increase of speed. In the past, the aerodynamic pass-by noise prediction was usually conducted with the wind tunnel mode, ignoring the Doppler effect. In this paper, an equivalent source method considering the Doppler effect is proposed to study the aerodynamic pass-by noise. A cylinder case is considered first to verify the effectiveness of the method. Then a DSA 380 pantograph of a Chinese high-speed train is considered. The pantograph is divided into three parts, and each part is equivalent to a monopole or dipole sound source. Results show that the upper part of the pantograph is closer to a dipole source, while the middle and lower parts are closer to a monopole source. When the measurement point is directly above the pantogragh, the contribution of the upper part is the largest, while for both sides measurement points of the pantograph, the contribution of the upper part is the smallest.

An optimization of sinusoidal rumble strip design parameters

Previous research has shown that rumble strips using a sinusoidal profile can reduce pass-by noise while creating equal or greater interior noise and vibration compared to more conventional discrete strips. Several different sinusoidal designs have been proposed and evaluated in previous research, however, a single design has yet to be confirmed. In the current research, 20 different sinusoidal designs were installed on a two-lane highway each with different parameters of wavelength, peak-to-peak amplitude, and recess below the existing pavement. The test matrix included wavelengths varying from 30.5 to 60.9 centimeters, peak-to-peak amplitudes from 7.9 to 12.7 millimeters, and recesses of 0 and 3.8 millimeters. Previous research has also shown that the performance of individual designs depends on the individual vehicles used in the testing. In this research, four vehicles of from each of four different design types were used and averaged together to judge the performance of the 20 rumble strip designs for pass-by noise, and interior noise and vibration. From this research, the recommended design is one with a 38.1 centimeters wavelength +/- 12.7 millimeters, no recess, and a peak-to-peak amplitude of 11.1 to 12.7 millimeters. The results used to justify this recommendation are presented in this paper.

Has the German vehicle fleet become quieter? - Results of a measurement campaign using SPB and CPX measurements

In the past, the German Environment Agency has carried out several measurement campaigns to determine the noise behavior of the German vehicle fleet. The aim of the current project was to identify any trends in comparison to previous campaigns. Autonomous pass-by measurements were carried out at 30 locations throughout Germany in accordance with DIN EN ISO 11819-1 (SPB) with the aim of recording at least 1000 vehicles per location. As the road surface influences the pass-by noise, near-field measurements according to DIN EN ISO 11819-2 (CPX) were carried out to determine the homogeneity of the road surface at each measurement location. In parallel to the CPX measurements, texture measurements according to DIN EN ISO 13473 were carried out to quantify the relevant geometric parameters of the road surface. The presentation describes the methodology of these measurements and presents the final results including a comparison with data from the 2012 and 2002 measurement campaigns.

Pass-by noise regulation - Uncertainties reduction thanks to tire sound emission modelling

The UN regulation R51-03 on vehicle sound emissions enters its third phase in July 2024, with the challenging level of 68 dB(A) to achieve for most of passenger cars and light commercial vehicles. The Lurban indicator, as calculated in the regulation, is a weighted average of acceleration and constant rolling speed tests. Thus, the tire sound emissions represent by far the first contributor to the vehicle compliance. Therefore, it is crucial to understand how tire sound changes under the effects of speed, acceleration, or temperature. In this paper, a study on tire sound behavior is presented. It is based on repeated measurements of pass-by sound emissions of a set of tires, under various conditions of speed, acceleration, and ambient temperature. Among a huge variety of tire sound emission models, a regression algorithm is used to identify the model that fits the best to the measured tire sound emissions data. This tire sound emission model is then used to foresee the impacts of Regulation R51-03 updates, aiming at reducing the uncertainties induced by temperature and test track discrepancies, by correcting the tire sound contribution. The effects of this correction on the uncertainties can be anticipated by the model.

A bottom-up numerical model for wheel-rail contact to predict rail-way noise emission

Pass-by noise emission models are often based on measurement databases, yielding engineering models that are fast enough to calculate noise maps or to do predictions based on existing infrastructure. However, these cannot predict the effect of innovative components, either in the track or in the rolling stock. Changing properties of a single component, e.g. damping of rail pads or the profile of a wheel, leads to a chain of coupled effects including the dynamics of the individual component, the contact force, the vibrational velocity, and finally the emitted noise. These intricate interactions can only be captured by detailed numerical models. We present a step-by-step implementation that allows to predict the effect of changes on the component level on the pass-by noise emission. The model includes the finite element calculation of the mobility of track and wheel separately, and uses these to derive the contact force from the combined roughness and train speed. Next, the vibration velocities of rails, sleepers, and wheels are used as input for a boundary element calculation of the noise emission. Pass-by measurement results validate the models, and show good agreement if wheel-rail contact noise is dominant and secondary sources can be ignored.

On application of sound power radiation of rolling tyre measured using CPX-based methodology

The present paper provides a comprehensive account of sound power radiation measurement from a rolling tyre, utilising a methodology that employs an advanced PolyU Mark III Close-Proximity (CPX) trailer enclosure which is aimed to provide CPX measurement per relevant ISO stsandard with suppressed background noise within the interior. The interior walls and ceiling of the enclosure are equipped with diffuser panels, creating a reverberant environment suitable for sound power measurement using the comparison method. The optimal design of the enclosure, which minimizes acoustic resonance and ensures a uniform distribution of acoustic energy, is determined through extensive numerical simulations. During tyre/road sound power measurements, the spatially averaged sound pressure level (SPL) distributions within the enclosure are obtained with a reference sound source (RSS) of known sound power. The relationships between the RSS SWLs and the corresponding SPLs are established at all vehicle speeds. These relationships can then be utilised to deduce the total SWL, as well as its 1/3-octave spectrum, from the captured averaged SPL radiated by a tyre rolling at any vehicle speed. The effectiveness of the CPX-based sound power measurement are illustrated. Additionally, the potential of utilising the measured SWLs for predicting pass-by noise radiation to roadside is discussed.

A review of vehicle speed measurement methods for the statistical pass-by noise testing

The Statistical Pass-By method (SPB, ISO11819-1) is used in environmental impact studies to evaluate, classify, and compare different road surfaces according to their influence on traffic noise. It relates the noise level to the type of vehicles and their speed. There are different methods to measure vehicle speed and the cost plays a significant role in their practicality and widespread adoption. Radar, Lidar, and Photocells-based method systems typically involve higher initial costs due to the sophisticated technology employed, but they offer real-time and accurate data, justifying their investment. On the other hand, Video camera systems may have lower initial costs, but their accuracy can be influenced by environmental conditions and calibration requirements. This paper will assess the cost-effectiveness of these technologies, considering not only the initial setup expenses but also maintenance and operational costs over time. Cost-benefit analyses are crucial in determining the most economical yet reliable solution for specific budget constraints. As the research in this field progresses, a key focus lies in optimizing the balance between cost and performance to make these systems more accessible and practical also for a wide range of applications, ensuring that advancements benefit both traffic management authorities and users alike.

The impact of tyre tread pattern design parameters on accelerated pass-by noise

Road-Traffic noise is one of the major environmental issues globally. Considering its effects on human health, international standards have been developed and emission limits have been adopted. In Europe, these regulations are becoming more stringent and challenging the automotive industry. There are two legislative Pass-by-noise test methods: Normal Pass-By-Noise (R117) for Tyre legislation and Accelerated Pass-By-Noise (R51) for vehicle legislation. For OE (Original Equipment) business meeting strict Accelerated Pass-By-Noise target is necessary for the Tyre industry because Tyre is a major influencing factor in overall vehicle noise. This paper explores the relationship between the parameters of tyre tread pattern and their effect on accelerated pass-by noise. The investigation shows how specific characteristics of the tread pattern, such as design, groove geometry, and other relevant factors, contribute to the overall noise generated during accelerated pass-by noise measurements.

Effective Low Noise Rumble Strip Design and Performance

The purpose of the NCHRP 15-68 Effective Low Noise Rumble Strips project research was to develop and recommend a rumble strip design to achieve somewhat conflicting goals. The design was to minimize the exterior noise that can affect residences along a roadway while producing sufficient interior noise and vibration inside the vehicle to alert the operator of a lane departure. Review of the previous research indicated that this could best be accomplished with a rumble strip of a sinusoidal profile. The first portion of this research was to develop a recommended test procedure which was presented at the 2022 TRB Annual Winter Meeting. Using this procedure, sinusoidal strips were tested in three different states, which included four different wavelengths, 12, 14, 18, and 24 in. The smallest of these produced sufficient interior noise and vibration; however, it produced higher levels of pass-by noise. The largest of these produced the lowest pass-by levels but insufficient interior noise and vibration relative to existing criteria. To explore the intermediate dimensions, 20 different designs of sinusoidal rumble strips were constructed and tested in Washington State. In addition to wavelength, the peak-to-peak dimension of the sinusoidal shape, and the amount that the shape was recessed relative to the existing pavement surface were tested. From the results of the testing of strips, a wavelength of 14 to 15 in., a peak-to-peak amplitude of 7/16 in., and no recess are recommended.

Aspects of rumble strip noise at distant ranges

One aspect of rumble strips that limits the use of these devices is noise intrusion for residents nearby the roadway. To investigate this issue as part of the NCHRP quieter rumble strip project, pass-by noise measurements on the rumble strips were made beyond the standard evaluation distance of 25 feet (7.5m). Distances varied from 48 feet (14.6m) to 381 feet (116m) more typical of distances for residences near the roadway. For this assessment, pass-by noise measurements and recordings on the rumble strips were made at distances using one test vehicle from the primary research. The measurements were for sinusoidal rumble strips with wavelengths of 13, 15, 16, and 17 inches (33.0, 38.1, 40.6, and 43.2cm). For comparison, measurements were also made for more standard, discrete grind rumble strips. For all strips, the frequency of the repetition rate was apparent as the vehicle approached the microphone location and to a lesser amount after the vehicle passed the microphone. It was also demonstrated that the overall A-weighted level fell-off at a higher rate than the level at the repetition rate. The 80 Hz tone from the sinusoidal strips was observed to be barely audible, unlike the 100 Hz tone for the conventional strips.

Methodology and Realization of Indoor Pass-by Noise measurement for passenger cars

Nowadays the protection of human life is extremely important, and for this purpose the vehicles must go through a homologation process before the introduction to market. If we look at the acoustical requirements, one of the most important test procedures is the Pass-by Noise (PBN) measurement, which defines the noise emission limit value, when the observer stands beside the vehicle passing him by. There are two versions: Exterior (or Outdoor) and Indoor (or In-room) Pass-by Noise (IPBN) measurement. Former is presently the only accepted method for homologation; however, environmental and weather conditions could strongly influence its feasibility. For this reason, IPBN got into focus, with better suitability for development purposes and the prospect, that it will be accepted later for the homologation process too. This paper focuses on the IPBN method: gives an overview on the setup and presents the details of a realized test-measurement campaign. Beside the 2 most important points: the measuring room and the position of the sensors, the measurement devices, vehicle location and connection to measurement system, the measuring program and the whole process are presented together with some preliminary results related to different characteristics of the vehicle.

Partial sound source estimation with Helmholtz inverse beamforming as a part of pass-by noise virtualization

Noise has an impact on human health. Therefore, pass-by noise of motor vehicles is legally regulated. The latest norm of the Economic Commission for Europe is ECE R51.03. According to this norm, pass-by noise of motor vehicles must be reduced to a sound pressure level of less or equal 68 dB(A). This poses a challenge for original equipment manufacturers. Firstly, they need a detailed analysis on the influence of contributing vehicle components such as engine, exhaust system and tires to the over-all pass-by noise. Secondly, original equipment manufacturers strive to shorten development cycles and lower production costs. Therefore, predictions of the expected physical behaviour of future cars have gained increasing importance. This leads to the emergence of new technological concepts like digital twins. This paper presents an extension of our latest approach to partial sound source analysis of simulated pass-by noise, i.e. Helmholtz Inverse Beamforming. Moreover, we present the embedding of the results of Helmholtz Inverse Beamforming in a comprehensive virtualization concept of pass-by noise engineering. By combining Helmholtz Inverse Beamforming with machine learning predictions of future cars, this concept enables us to derive target values of acoustic components regarding their pass-by noise.

AI-based method for determining vehicles with illegal muffler from pass-by noise

In Japan, illegal noisy vehicle is controlled by the result of a stationary noise test. The stationary noise test used does not have a simple correlation with pass-by noise due to differences in vehicle conditions. If illegal vehicles can be identified by pass-by noise, it will lead to more effective roadside inspections. Therefore, this study investigated whether it is possible to identify vehicles that exceed the limit value of the stationary noise test limit from pass-by noise using AI. First, we investigated the method using a single sound level meter, and then considered the use of a microphone array to make the method more effective in road traffic flow.

FE-based Simulation of Radiated Noise for a Rotating Tire

Today, the significance of reducing pass-by noise is increasing steadily due to EU labeling regulations and the demands of car makers. As a result, numerous companies are actively conducting research to minimize pass-by noise. In this paper, we introduce a finite element method (FEM) prediction technique for reducing pass-by noise, aimed at reducing the time and cost involved in manufacturing, testing, and verifying pass-by noise. We have created a tire FE model that incorporates the full pitch sequence of the tire pattern, and used it to predict airborne noise (ABN) generated by air pumping and vibration due to the grooves in the pattern. The simulation environment was designed to match the test conditions in Hankook's anechoic chamber, and we compared the frequency spectrum of the simulation results with the actual test results. In conclusion, we have successfully performed FEM simulation of radiated noise, which accurately reflects the noise generation mechanism of rotating tires. This has improved the simulation accuracy for predicting airborne noise.

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.

Recent research advances on high-speed railway noise

Around 42,000 km high-speed railways are in operation in China at speeds up to 350 km/h. 400 km/h trains are also under development. Huge resources have been put into research on high-speed railway noise. This paper outlines advances achieved in several key projects by covering the following aspects: measurement results showing typical characteristics of high-speed railway noise; analyses on source contribution to pass-by noise based microphone array data; modelling of high-speed rolling, aerodynamic and viaduct bridge noise; prediction of the vibro-acoustic behaviour of car-body with poro-elastic media; and finally, analyses of vibration transmission in the suspension/bogie system.

Study on the relationship between the basic physical characteristics of ISO road surfaces and tyre noise

As vehicle electrification progresses, the contribution and importance of tyre noise to Pass-by noise is increasing. In general, tyre noise level varies depending on the road surface and it is known that even on road surfaces that satisfy ISO10844 (Specification of test tracks for measuring sound emitted by road vehicles and their tyres), coasting tyre rolling sound fluctuates by a few decibels. For that reason, the measurement uncertainty of tyre noise due to the difference in road surfaces has become unignorable. For further reduction of road traffic noise, it is necessary to understand the relationship between basic physical characteristics related to road surfaces and tyre noise that contribute to measurement uncertainty. In this study, we constructed several road surfaces with different construction methods within the range of ISO10844 and investigated the relationship between them. In this report, we show the results of our efforts, including knowledge that is not standardized by ISO10844.

On site acoustical characterization of a removable urban pavement with functionalized surface

Removable urban pavement consists in an assembly of cement concrete slabs that can be easily removed or replaced for maintenance purposes. Within the I-STREET CUD-SF project, a removable urban pavement with functionalized surface was implemented in the inner city of Nantes in France. The slabs are made of cement concrete with a dense body and a porous top layer of grading 0/6 and porosity 25%, enabling water drainage and sound absorption. The demonstrator was approximately 31 m long by 6 m wide. Road surface texture was measured in 3D, leading to classical texture indicators and assessment of irregularities at the junction between slabs. Sound absorption was also measured by the extended surface method. Noise performance of the pavement was assessed at 30 km/h by the Statistical Pass-By and the Close-Proximity methods. Pass-by noise level was reduced by 2.3 dBA by comparison with the old pavement. Close-Proximity noise levels have shown a reduction of 3.4 dBA by comparison with an old DAC 0/10. The noise abatement is mainly due to a decrease in the frequency range between 800 Hz and 1600 Hz. Noise measurements will be repeated after one year to highlight a possible evolution of acoustical performance.

A simulation and diagnosis of tire radiation noise

Due to the recent pass-by noise regulation, reduction of tire noise has been being required. In order to meet the requirements of the regulation, it is important to simulate and diagnose tire radiation noise for efficiently finding a quieter tire structure. In this paper, an accurate simulation model is employed. With the model tire radiation physics are diagnosed by patch contribution and wavenumber contribution. The diagnosis showed that radiation was dominantly generated at near contact patch and lower wavenumber component dominantly contributed to radiation. In order to further diagnose about what behavior contributes, an approach that calculates radiation efficiency of wavetypes is proposed. The proposed approach finds high radiation efficiency wavetypes at each frequencies so that behavior of highly contributing to radiation at frequencies of interest can efficiently be found, which helps designers to think about design modification to reduce tire radiation noise.

A novel position estimation method for wayside pass-by noise sources based on Doppler effect correction

The localization of moving noise sources has garnered substantial attention in recent years, prompting researchers to develop a range of methodologies for positioning sound sources across diverse scenarios. Despite this progress, the intricate interplay of complex spatial sound fields and the Doppler effect during motion presents a formidable challenge in achieving accurate sound source localization. To address these challenges, this paper proposes a novel method for estimating positions of wayside pass-by noise sources based on Doppler Effect Correction (Do-bPE). The proposed method capitalizes on a spatial microphone array to capture signals emanating from moving sound sources. Each channel’s sound signal is transformed into the time–frequency domain using Short Time Fourier Transform (STFT). The Approximate Greatest Common Divisor (AGCD) algorithm is then applied to extract the instantaneous frequency of the moving source from the time–frequency spectrogram. By leveraging nonlinear least squares fitting and the acoustic Doppler model, this instantaneous frequency facilitates the kinematic parameters estimation of Doppler effect, which provides the distances between each microphone within the array and the trajectory of moving sound source. Then, by employing the weighted least squares method to solve the relationship between the sound source and the array microphones, an accurate spatial position for the sound source can be obtained. The method successfully applies the Doppler effect to estimate the source distances, subsequently refining position estimation accuracy through microphone array processing. Simulation and experimental results show that the method’s positioning accuracy and robustness are significantly improved compared to existing approaches.