Automotive Tire Noise and Vibrations

Analysis, Measurement and Simulation

Xu Wang

• Publisher: Butterworth-Heinemann
• Year: 2020
• ISBN:
  9780128184103
• Topic: Technology & Engineering
• Subtopic: Automotive Transportation & Engineering
• Index: Technology & Engineering

Automotive Tire Noise and Vibrations: Analysis, Measurement and Simulation presents the latest generation mechanisms of tire/road noise. The book focuses not only on tire/road noise issues from the tire/road structures, materials and dynamics, but also from a whole vehicle system. The analyses cover finite element modeling, mathematical simulations and experimental tests, including works done to mitigate noise. This book provides a summary of tire noise and vibration research, with a focus on new simulation and measurement techniques.

• Covers new measurements techniques and simulation strategies that are critical in accurately assessing tire noise and vibration
• Provides recent simulation progress and findings of CAE on analysis of generation mechanisms of the tire/road noise
• Features a Statistical Energy Analysis (SEA) and model of a multilayer trim to enhance the sound absorption of tire/road noise

Chapter 1

Background introduction

Xu Wang, School of Engineering, RMIT University, Melbourne, VIC, Australia

Abstract

The definition, classification, and history of tire/road noise have been introduced. Terminology of tire/road noise has been defined. The chapter structure of this book has been outlined. The objective of this book is to introduce the subject of the tire/road noise, to define terminology, and to connect different disciplines involved. The uniqueness of this book is to study the tire/road noise in the system of road, tire, and vehicle suspension as a whole, which is different from other books related to this topic.

Keywords

Tire/road noise; A-weighted; sound pressure level; pass-by noise; interior noise; exterior noise; airborne noise; structure-borne noise; transfer path analysis; generation mechanism; characteristics; source strength; acoustic transfer function; regulation; mean profile depth; tread pattern; road surface

Sound results from small, fast pressure variations and propagates in a fluid medium. Acoustics is a science of sound that studies generation, propagation, and reception of sound in all aspects. Noise is refereed as unwanted sound. In the case of the tire/pavement noise, the unwanted sound propagates in the medium of the air. Thus any air pressure variation resulting from the tire/road interaction will generate noise in the air. The traffic noise was commonly already complained in the Roman Empire. Nearly 2000 years later, in 1869, the problem seemed not to be changed much, as noted by Sir Norman Moore, a British physician, who described the noise graphically in a London street: “Most of the streets were paved with granite sets and on them the wagons with iron-tired wheels made a din that prevented conversation while they passed by. The roar of London by day was almost terrible—a never varying deep rumble that made a background to all other sounds” [1].

Tire/road noise (TRN) is the noise emitted from a rolling tire as a result of the interaction between the tire and road surface [2]. TRN is also known as the tire–road interaction noise, tire–pavement interaction noise (TPIN), tire–pavement noise, or tire noise. The term tire/tyre was used even before the pneumatic tire was known representing the outer part of the wheel. In the days of iron-shredded wheel/tires, the interaction of metal (tire as well as horse shoes) and stone (pavement) created noise.

TRN includes two aspects, one is the interior TRN, which has been concerned with vehicle engineers and tire industry from the 1930s, and the other is exterior TRN, which was first studied experimentally in 1955 [3].

The success in reducing the vehicle interior TRN has been remarkable. For example, the interior dominated TRN levels in the 1.5–1.8 liter Japanese cars driven at 100 km/h had been reduced by 8 dB(A) in the time period 1976–85 [4]. Sound pressure levels (SPLs) and sound quality of the interior TRN have been reduced and improved. The reason for the remarkable reduction of interior noise is that the acoustic comfort within a vehicle cabin is one of the important product quality attributes reflecting the brand image: vehicles that are quiet inside are considered comfortable and give the owner a feeling of luxury.

Interior TRN is affected by tire, road, and vehicle suspension system. The TRN is generated by four subsources/mechanisms: tread impact, air pumping, slip-stick, and stick-snap. At the tire–pavement interaction, the mechanisms create energy, which is eventually radiated as sound. The four TRN source generation mechanisms are all important for certain combinations of the tire and pavement. Different source mechanisms may dominate the sound generation for different applications making it difficult to develop the TRN reduction strategies for all cases. If source mechanisms are similar in strength, a strategy to suppress one mechanism will not have a large effect on the overall noise level because other mechanisms will become dominant. Sound enhancement mechanisms are the characteristics of the TPIN that causes that energy to be converted to sound and radiated efficiently. The sound enhancement mechanisms consist of the horn effect, organ pipes, the Helmholtz resonators, carcass vibration, and internal acoustic cavity resonance. The enhancement mechanisms further complicate the strategies for reducing the TRN. The contributions from the various sound enhancement mechanisms or from the source mechanisms are often difficult to distinguish from each other. It is not clear which mechanisms are important for various surfaces and conditions. Many of the mechanisms for generation or enhancement of the sound from tires and road are directly integrated with the tire/road characteristics required for safety, durability, and cost.

The road traffic noise is a main contributor to environmental noise, which represents a burden to people resulting in annoyance, sleep disturbance, or cardiovascular disease [5]. Hence, legislation intends to reduce and limit vehicle exterior noise [6] in order to increase health and life quality. Modeling/analysis, measurement, and simulation techniques of the exterior TRN have been extensively studied since the 1970s. The emission limits introduced first in the 70s were very liberal, but later tightening of limits has been rather tough, at least for trucks and busses. Exterior vehicle noise has been reduced very little at high speeds but largely at low speeds for heavy vehicles. But the exterior TRN of the passenger car tires may have increased somewhat rather than decreased; the reasons for this issue are believed to be caused by no requirements being in place and a general trend toward wider tires with design optimizations more and more focused on their extreme high-speed performance.

In 1982 Samuels [7] conducted systematically experimental studies and theoretical study named as air-pumping theoretical model, and derived some important conclusions, which are now also correct and guiding: (1) Roadside noise level increased with increasing vehicle speed, road surface macrotexture roughness, and tire tread roughness. (2) The road surface macrotexture was found to be the most dominant of the above three parameters. (3) The roadside noise contributed from different road and tire components occurred over different frequency ranges.

Speed, road, and tire are the three most important and dominant factors for exterior TRN. No other single factor has a more prominent influence on TRN than the speed. It is well known that the noise relationship with vehicle speed very closely follows the ideal relation L_p=A+B×log(V) as V is the vehicle speed in unit of km/h. However, the speed influence is not our focus for the solution. Therefore the noise–speed relation is seldom outlooked any further.

With regard to the road surface, different road surfaces may give a large variation in noise levels, say up to 17 dB(A) [8]. A driver can easily have this driving experience on different road surfaces. The rougher the texture is, the higher the noise emission becomes. The mean profile depth (MPD) for the road surface texture has been found to be a good measure of the road surface texture for describing its influence on wet friction, but unfortunately it appears that the relation between the noise level and MPD is far from being clear.

Tire influence has a SPL range of 10 dB(A) between the best and the worst tires in a sample of nearly 100 tires of approximately similar sizes (the tires were all new or newly retreaded and available in tire shops) [8]. In addition to the SPL range quoted above, other variables like tire width and state of wear also affect the TRN levels and will increase the flouncing range of the TRN SPLs. When taking all such effects into account, it seems that the flouncing range of the TRN SPLs for tires is approximately as large as that for road surfaces.

The TRN emission should always be eliminated at the source. It is natural to look first at the possibilities for the noise reduction through the measures relating to tires. It is important to understand the root causes and generation mechanisms of the TRN to reduce the noise.

Background introduction of TRN is concluded here. Chapter 2, Tire/Road Noise Separation: Tread Pattern Noise and Road Texture Noise, will introduce close proximity (CPX) method to measure the near-field TRN and break down the tire noise into the tread pattern and nontread pattern noise components. This method can also be expanded to lab drum test applications where the noise can be separated into tread pattern noise, road-drum noise, and aerodynamic noise. Chapter 3, Influence of Tread Pattern on Tire/Road Noise, studies the contribution of tread pattern to TRN through two major mechanisms: (1) tread impact due to the interaction between the tread blocks and the road and (2) air pumping due to the air compression/expansion in the tread grooves.

Chapter 4, Influence of Road Texture on Tire/Road Noise, investigates influence of road surface on the TRN. It was found that smoother pavement tends to cause higher tread pattern noise but lower nontread pattern noise. Good correlation can be found between pavement texture velocity spectrum and tire nontread pattern noise spectrum. Chapter 5, Measurement Methods of Tire/Road Noise, studies measurement methods of the TRN as not only objective measurements but also advanced subjective evaluations will have to be conducted to evaluate and quantify the TRN. Different indoor and outdoor tests developed over years and used by industry and academia are presented to evaluate tire noise and vibration performance in regard to their generation and transmission. Chapter 6, Generation Mechanism of Tire/Road Noise, studies the generation mechanisms of the TRN. The tire noise and vibration and their different mechanisms involved in generation, transmission, as well as amplification of the structural borne noise and the airborne noise to the vehicle cabin and the environment will be illustrated. Chapter 7, Suspension Vibration and Transfer Path Analysis, will study the excitation of suspension, which mainly comes from the tire–road roughness and tire or tire–pavement interaction. Chapter 7, Suspension Vibration and Transfer Path Analysis, will also study the method of transfer path analysis (TPA) and the application of TPA method in analysis of structure-borne TRN. Chapter 8, Structure-Borne Vibration of Tire, will investigate the modal characteristics of tire and the influences of some key parameters on the modal characteristics, including the inflation pressure, tread pattern, tire mass, belt angle, and Young’s moduli of belt cord and tread compound. The modal testing method, analytical modal models, and finite element model of a tire (including 2D and 3D ring models) will be also studied. Chapter 9, Structural-Acoustic Analysis of Tire-Cavity System, will explore tire-cavity noise by means of analytical, finite element, and experimental methods.

Chapter 10, Computer-Aided Engineering Findings on the Physics of Tire/Road Noise, will report the progress and improvement in the theory and algorithms that is being used to simulate and predict the TRN including the key CAE simulation methods like finite element method (FEM), boundary element method (BEM), waveguide finite element method (WFEM), statistical energy analysis (SEA), energy finite element analysis (EFEA), computational fluid dynamics (CFD), and TPA. This chapter also studies the auralization models of the TRN and uncovers the current trends and challenges in the CAE modeling of TRN. Chapter 11, Tire/Road Noise Mitigation Using Acoustic Absorbent Materials, will study the acoustic properties of felt material by means of theoretical calculation, finite element simulation, and laboratory experiment. Chapter 11, Tire/Road Noise Mitigation Using Acoustic Absorbent Materials, will also investigate possibility of the use of felt and multilayer trim materials for increasing the acoustic damping and sound absorption coefficient of cavities through a given mathematical solution and several empirical models found in the literature and verify it by the impedance tube measurement results.

Chapter 12, Statistical Energy Analysis of Tire/Road Noise, will study the basic principle of SEA and the application of SEA method in analyzing TRN, which includes the subsystem parameter identification, and the mean energy prediction of all the airborne and structure-borne TRN subsystems in the mid-high frequency range.

Chapter 13, Pass-by Noise: Regulation and Measurement, will study general vehicle pass-by noise with a focus on generation mechanisms, characteristics, and frequency components of the pass-by TRN. Chapter 14, Pass-by Noise: Simulation and Analysis, will introduce the simulation, analysis, regulation testing, and numerical prediction methods of the pass-by noise for source identification and sensitivity study based on the TPA method.

Chapter 15, Summary and Future Scope, will make conclusions for this book. The TRN is generated by the impact of road surface texture on the tire tread and by the impact of the tire tread pattern on the road surface, both of these exciting radial vibrations in the tire. In addition, the displacement of air in and out of the tire–pavement interaction contact patch contributes to the noise emission. Chapter 15, Summary and Future Scope, will also illustrate the future research scope of the TRN including how electric ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• Preface
• Chapter 1. Background introduction
• Chapter 2. Tire/road noise separation: tread pattern noise and road texture noise
• Chapter 3. Influence of tread pattern on tire/road noise
• Chapter 4. Influence of road texture on tire/road noise
• Chapter 5. Measurement methods of tire/road noise
• Chapter 6. Generation mechanisms of tire/road noise
• Chapter 7. Suspension vibration and transfer path analysis
• Chapter 8. Structure-borne vibration of tire
• Chapter 9. Structural-acoustic analysis of tire cavity system
• Chapter 10. Computer-aided engineering findings on the physics of tire/road noise
• Chapter 11. Tire cavity noise mitigation using acoustic absorbent materials
• Chapter 12. Statistical energy analysis of tire/road noise
• Chapter 13. Pass-by noise: regulation and measurement
• Chapter 14. Pass-by noise: simulation and analysis
• Chapter 15. Summary and future scope
• Index