Tire Noise Research Articles

Tire Noise Analysis during Vehicle Acceleration Running with Acoustical Holography (2nd Report, Noise Source Identification by 2-Dimensional Arrayed Microphone Method)

In order to analyze the tire noise emission during vehicle acceleration running, noise source detecting method with acoustical holography was applied to vehicle acceleration running condition, which was developed to constant speed running. This paper describes the effectiveness of 2-dimensional arrayed microphone method by simulated calculation and the experiments with model noise sources, and propose the new method to identify the noise source without valid information on noise source frequency, which is pure tone or broadband noise.

Estimating traffic noise for inclined roads with freely flowing traffic

Traffic noise measurements on the kerbs of 19 independent inclined trunk roads with freely flowing traffic within the residential areas of Hong Kong are carried out in the present investigation. The performance of the existing noise prediction models in predicting traffic noise from inclined roads is evaluated. By regression analysis and simple physical consideration of the traffic noise production mechanisms, formulae for the prediction of the L A10, L A50, L A90 and L Aeq are developed or re-calibrated. Results suggest tyre noise has the major contribution to the overall noise environment when the source is an inclined trunk road. Also, the road gradient is found to have a higher contribution to the traffic noise than assumed in the existing models, but becomes unimportant when the background noise level L A90 is concerned.

Theory on Pitch Noise and Its Application

A theory on pitch noise of a tire has been developed based on the assumption that noise is approximated by a series of Dirac delta-function. The proposed theory predicts the existence of special lug shapes where tire noise becomes almost zero. In addition a tire noise simulation system is developed based on this theory to predict tire noise from CAD data. The prediction of overall noise of various tires with practical patterns is verified to be in good agreement with the measurement.

Performance of iterative solvers for acoustic problems. Part II. Acceleration by ILU-type preconditioner

We are presenting an incomplete factorization preconditioner for the boundary integral formulation of the time harmonic Helmholtz equation in 3D. Out of the matrix of the near field interactions of a Fast Boundary Element Method, we are constructing the preconditioner using an incomplete LU-factorization provided in the SPARSKIT V. 2 package by Saad. This preconditioner is tested and discussed for Restarted GMRes and for CGNR. Application showed little influence on internal problems. Therefore, the paper is dedicated to external problems only. These problems solved by the hypersingular formulation of Burton and Miller is strongly affected by this preconditioner. Especially for non-smooth surfaces, the preconditioner reduces the number of iterations needed by GMRes or CGNR significantly. Examples that are investigated are a cat's eye, a tire noise problem and a piston compressor.

Performance of iterative solvers for acoustic problems. Part I. Solvers and effect of diagonal preconditioning

Boundary element discretization of the Kirchhoff–Helmholtz integral equation gives rise to a linear system of equations. This system may be solved directly or iteratively. Application of direct solvers is quite common but turns out to be inefficient for large scale problem with 10,000 unknowns and more. These systems can be solved on behalf of iterative methods. This paper is dedicated to testing performance of four iterative solvers being the Restarted Bi-Conjugate Gradient Stabilized algorithm, the Conjugate Gradient method applied to the normal equations (CGNR), the Generalized Minimal Residual (GMRes) and the Transpose Free Quasi Minimal Residual. For that, we distinguish between internal and external problems. Performance of iterative solvers with respect to problem size, polynomial degree of interpolation, wave-number, wave-number over problem size, absorption at surface, and smoothness of the surface is investigated. Furthermore, the effect of diagonal preconditioning is illuminated. All examples consist of different meshes of up to more than 100,000 elements. In general, the methods perform well for the internal problems, a duct problem, a sedan cabin compartment and a fictitious small concert hall. GMRes proves to solve the problems most efficiently. External problems appear more challenging due to the hypersingular operator of the Burton and Miller formulation. Scattering of a plane wave at a sphere and at a cat's eye are investigated as well as a tire noise problem. The first two are remarkably efficiently solved in the medium and high frequency range by CGNR whereas the tire noise example is only solved by GMRes. In all examples, at least one or two solution methods turn out to require less operations than a direct solver. The effect of diagonal preconditioning is marginal especially for higher frequencies.

Tire Noise Analysis during Vehicle Acceleration Running with Acoustical Holography.

In order to analyze the tire noise emission during vehicle acceleration running, noise source detecting method with acoustical holography was applied to vehicle acceleration running condition, which was developed to constant speed running. This paper describes the effectiveness of this method by simulated calculation and the analysis results of the tire noise sources during acceleration running for the electrical vehicle with the test tires.

Use of compliant adhesive layers in direct glazing of road vehicles for improved sound attenuation

Particularly at low speeds and on poor road surfaces, the noise level inside a moving vehicle is determined to a significant degree by tyre noise in the low-frequency range (up to 500 Hz). Vibrations transmitted from the tyres to the window glass via sound bridges produce pressure oscillations inside the passenger compartment which are perceived by the vehicle occupants as noise. Finite element calculations, which are confirmed by test results, show that these oscillation can be reduced by the use of a windshield adhesive with a low modulus of elasticity and good damping characteristics. The test results show that the most effective way of improving the acoustics inside the passenger compartment is to employ a two-phase windshield adhesive applied by the coextrusion method. Experimental modal analysis shows that the use of a two-phase adhesive applied by the coextrusion method and incorporating a low-viscosity core can dramatically lower the overall level of vibrations in the window glass by 30–50 per cent, and in particular can bring about a flattening of the resonance peaks in the all-important roll vibration range between 100 and 500 Hz. This results in a reduction in sound levels within this frequency range of between 1 and 2 dB for rear-seat passengers.

Sound source reconstruction using inverse boundary element calculations.

Whereas standard boundary element calculations focus on the forward problem of computing the radiated acoustic field from a vibrating structure, the aim in this work is to reverse the process, i.e., to determine vibration from acoustic field data. This inverse problem is brought on a form suited for solution by means of an inverse boundary element method. Since the numerical treatment of the inverse source reconstruction results in a discrete ill-posed problem, regularization is imposed to avoid unstable solutions dominated by errors. In the present work the emphasis is on Tikhonov regularization and parameter-choice methods not requiring an error-norm estimate for choosing the right amount of regularization. Several parameter-choice strategies have been presented lately, but it still remains to be seen how well these can handle industrial applications with real measurement data. In the present work it is demonstrated that the L-curve criterion is robust with respect to the errors in a real measurement situation. In particular, it is shown that the L-curve criterion is superior to the more conventional generalized cross-validation (GCV) approach for the present tire noise studies.

Optimization of pitch sequencing for pneumatic tire by tabu search method

The reduction of tire noise has been an important research field in tire industry. The sequence design of tire tread blocks with different pitches is the primary way to reduce the objectionable noise level. In this paper, the optimization of pitch sequence around the tire circumference by tabu search has been implemented so that the maximum noise index over all harmonics is minimized. The pitch sequence of two tires has been examined. The result has shown that the maximum noise index of harmonics and the magnitude of power spectrum density of tire noise can be reduced remarkably.

ON THE HORN EFFECT OF A TYRE/ROAD INTERFACE, PART II: ASYMPTOTIC THEORIES

In Part I, it was shown that boundary element method calculations could successfully be applied to determine sound amplification by a tyre/road geometry. However, the computations are expensive, limited to frequencies below 2500 Hz, and provide little physical insight. In Part II, two supplementary asymptotic approaches are developed; a ray theory for high frequencies and a compact body scattering model for low frequencies. When tested on a representative tyre geometry, these methods are found to have excellent predictive capabilities, at frequencies above 3k Hz and below 300 Hz respectively. Furthermore, the ray theory shows that the neglect of curvature in Ronneberger's wedge model (1989 Workshop on Rolling Noise Generation, Institut fur Technische Akustik, Technische Universitat, Berlin) leads to erroneous amplification levels and interference effects, and the scattering model intriguingly predicts that low frequency amplification increases with belt width independently of the tyre diameter. Lastly, this work confirms the importance of numerical calculations for the intermediate frequencies, where tyre noise is most significant.

Traffic Noise — Experts Target Tyres

A Working Party of the International Institute of Noise Control Engineering (I-INCE) has studied the long-term success of international vehicle noise regulations on reducing road traffic noise. The Working Party, which had 13 members from 10 countries, concluded that there will be little further progress until tire noise is controlled.1

Visualization of pass-by noise by means of moving frame acoustic holography.

The noise generated by pass-by test (ISO 362) was visualized. The moving frame acoustic holography was improved to visualize the pass-by noise and predict its level. The proposed method allowed us to visualize tire and engine noise generated by pass-by test based on the following assumption; the noise can be assumed to be quasistationary. This is first because the speed change during the period of our interest is negligible and second because the frequency change of the noise is also negligible. The proposed method was verified by a controlled loud speaker experiment. Effects of running condition, e.g., accelerating according to ISO 362, cruising at constant speed, and coasting down, on the radiated noise were also visualized. The visualized results show where the tire noise is generated and how it propagates.

Experimental Modeling Techniques for Understanding Road Noise

Low frequency road noise phenomena in passenger vehicles have generic characteristics associated with tyre, suspension and body dynamics for a wide range of vehicle styles and classes. Experience has shown that transmission path concepts are inappropriate due to low modal densities and that understanding road noise requires a modal approach. The current techniques for experimental modal acquisition are limited by non-linearities of the suspension and tyre dynamics. Likewise the analysis processes are limited containing ‘ noise’ as a result of statistical variance, high levels of modal damping, and a complex force generation mechanism. In the fields of modal analysis and operational measurements MIRA has developed a number of experimental techniques to overcome some of the current limitations and provide a better understanding of the interaction between suspension and tyre dynamics within the typical operating environment. With a good understanding of both the natural and forced modes of the suspension system it will be possible to optimise the design of future suspension systems for NVH. MIRA has been involved in the measurement and development of suspension systems for road noise for many years. Road and tyre noise is increasingly a subjectively dominant part of the in-vehicle noise for a wide range of vehicles, particularly at low and mid- speeds. Analysis of the in-vehicle noise field for road induced noise has shown that the 63 and 125 Hz octave bands are both significant contributors to the total acoustic energy and correlate strongly with the subjective perception of low frequency tyre noise. Experience has shown that, not surprisingly, most of the energy in this frequency range is structure-borne. To better understand the structural paths MIRA has employed many of the techniques traditionally available to NVH development engineers such as Transfer Path Analysis (TPA), Principal Component Analysis (PCA), and virtual running mode analysis. These techniques have been specifically developed to address the analysis of multiple incoherent sources. Whilst these have proven invaluable in identifying major paths and have helped to

AN EFFICIENT PROCEDURE FOR VISUALIZING THE SOUND FIELD RADIATED BY VEHICLES DURING STANDARDIZED PASSBY TESTS

Throughout the world, motor vehicles are required to conform to statutory passby noise requirements. These standards usually entail the measurement of the peak A-weighted sound level while the vehicle accelerates past a stationary microphone. This pass-or-fail test is of little diagnostic value when a vehicle exceeds the statutory level. In the work presented here it is shown that a stationary array of microphones may be used to visualize the location of the noise sources on a vehicle executing a standard passby test. By locating the positions of the sources that dominate the received sideline levels, noise control efforts may be directed appropriately and efficiently. In the present work, a delay-and-sum beamformer approach was used to detect noise source locations. Algorithms have been included to correct the apparent source frequency shifts that result from the source motion. The restoration and de-Dopplerization procedure is based on using a polynomial representation of the source velocity (inferred in the first instance from a radar signal). Forward and backward propagation procedures are compared in terms of computational expense. In addition, a spherical spreading correction factor is described, along with a maximum likelihood procedure for obtaining an optimal array weighting dependent on the relative distance between the microphones and the focus point. The new weighting factor is compared with a more “intuitive” weighting factor and it will be shown that the new approach can reduce the sidelobe levels by comparison with the more intuitive approach. Experimental results presented here were based on the use of a 16 element, sparse array. It will be shown that this array could be used to identify the location and directivity of tire noise sources and of other sources on accelerating vehicles.

Traffic monitoring by tire noise

Presents the results of work of Planning Systems Inc. performed in fulfilment of the requirements of a Small Business Innovative Research (SBIR) Phase I feasibility study for the Federal Highway Administration (FHWA). The feasibility of developing an acoustic sensing technique to replace the current electro-mechanical (loop detector, tape switch, pneumatic tube) based methods of collecting vehicle axle passages was investigated. We exploit the fact that the dominate source of road noise is the broadband acoustic energy radiated by vehicle tyres by cross-correlating the outputs of spatially separated roadside microphones. The results demonstrate the feasibility of detecting vehicle passages by the cross correlation processing of radiated tire noise. The technique is based on technology developed as a consequence of our work in underwater acoustic signal processing.

Application and extension of acoustic holography techniques for tire noise investigations

Acoustic holography (AH) is a powerful measurement tool for the investigation of complex sound radiation problems. Enabling detailed source investigations based on noncontact measurements, it is especially useful for the investigation of rotating noise sources such as automotive tires. Nevertheless, conventional AH techniques are burdened by the constraint that the source is assumed to be planar. Based on a detailed measurement series which was performed on a laboratory roller bench, the radiation of a test tire was investigated by means of AH. It was found that even though valuable information could be obtained, the most important forward and backward radiation of the tire is difficult to tackle in this way. Another approach of the radiation analysis is offered by developing an inverse BEM method. Different implementations of the method have been worked out and tested, based mainly on the sysnoise and matlab software packages. The technique is applied to experimental tire mock-ups as well as to real-life tire measurements. The practical application and inherent limitations of the technique are also discussed.

A mathematical model of tyre noise generation

The paper presents an acoustic rolling model formulated in the time domain. The model describes a smooth tyre rolling on a rough surface, and consists of three parts. The first part is a theoretical description of the vibrational behaviour of tyres. Although one can rely on fundamental work, a simplified model is presented which limits computational effort, but is sufficiently accurate in the low and middle frequency range. The second part describes the contact between tyre and road. A bedding model is used for the tread and a time iterative solution method applied to the nonlinear problem. The last step is the calculation of the radiated sound caused by a vibration of the tyre belt, taking into account the geometrical condition (i.e. tyre and road represent together a horn). This step is solved by the application of the multiple synthesis. The results of the model are compared with measurements.

The investigation of a towed trailer test for passenger tire coast-by noise measurement

It is difficult to quantify the portion of coasting vehicle noise that is due to tire-pavement interaction alone. There are often contributions from aerodynamic noise of the vehicle, transmission whine, noise from suspension components, and other miscellaneous sources. The towed-trailer method used in the revised SAE J-57 standard has been shown to be an effective means of isolating tire-pavement noise for truck tires. This paper reports the results of a test program conducted by SAE Tire Noise Standards Committee to evaluate the feasibility of towed-trailer coast-by testing of passenger and light truck tires. The results of tests conducted in April 1996 at the Ohio Transportation Research Center are described and they indicate that accurate measurements are possible for towed-trailer testing of passenger tires. It is shown that a key aspect of performing such a test is reducing the noise of the tow vehicle and that sufficient reduction is possible even for quiet test tires. During the period of this work, the ISO/TC 31/WG 3 working group developed a draft trailer test method for evaluating tire noise. This test procedure was also evaluated. The results show the proposed test method to be highly accurate for tire noise evaluation.

The influence of belt and tread band stiffness on the tire noise generation mechanisms

A brief introduction to a theoretical model is presented which describes a smooth tire rolling on a rough road surface. The model is limited to a two-dimensional contact between tire and road. It includes the vibration properties of the tire, the nonlinear contact, and the sound radiation. It is also taking into account the influence of the acoustic properties of the road surface. The model is applied to determine the sound radiated due to the tire vibrations and the local deformations of the tread band. A parameter study is presented which shows the influence of the bending stiffness of the belt and the stiffness of the tread band on the noise generation and radiation mechanisms. The study also considers the influence of the surface roughness of the road. In this way it is possible to quantify which part of the roughness spectrum is leading to sound generation via tire vibration and which part of the roughness spectrum is involved in the local deformation of the tread band.

Computational and subjective procedures for the assessment of sounds with weak tonal components

A discrete tone is defined as ‘‘prominent’’ if the level of the tone exceeds the level of the noise contained in its critical band by 6 dB. Tonal or narrow-band noise components of tire sounds often fall short of this level, but are nevertheless rated as prominent by test drivers. Tonality is closely related to the sensation of pitch strength, which depends upon the sensation level, bandwidth, duration, and frequency of the tonal components present. In order to compare a number of computational procedures for calculating the tonality of sounds, a broad range of tire noises, synthesized tire sounds, and artificial tone–noise mixtures in which the level and bandwidth of the tonal components was varied, were subjectively assessed using (a) a paired-comparison technique, and (b) categorical judgments collected from about 60 listeners. They were objectively assessed by tone-to-noise and prominence-ratio measurements, and by a new method based on a model of pitch sensation which accounts for the temporal and frequency resolution as well as for masking properties of the human ear. The advantages and limits of the different methods will be compared and discussed. Especially for weak narrow-band components, the pitch model seems to be superior to the other methods used to quantify the degree of tonality.