Automotive Tire Noise and Vibrations: Analysis, Measurement and Simulation

By Xu Wang

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

• Language: English
• Publisher: Elsevier Science
• Release date: Jul 29, 2020
• ISBN: 9780128184103

Book preview

Australia

Preface

As developed powertrains become quieter and quieter, tire/road noise cannot be masked by the powertrain noise anymore. Therefore, tire/road noise of motor vehicles is increasingly important for the automotive industry and is a major concern for both vehicle manufacturers and component suppliers since legislation on noise pollution is driving down vehicle exterior noise, and customers are becoming more concerned about vehicle interior noise.

This book provides a review of tire/road noise generation mechanisms, characteristics, frequency contents, traffic regulation, control methods, advanced experimental and modeling techniques. A comprehensive reference list is provided in order to direct further studies and assist readers to develop in-depth knowledge of the sources and transmission mechanisms of the tire/road noise. The book aims to provide the information needed for university undergraduates and postgraduates, research students, scientific researchers, academia in mechanical or automotive engineering, highway and automotive engineers, and government officers related to environmental policies. The book could also be used as a textbook for postgraduate by course students in a program of mechanical or automotive engineering.

The tire/road noise is a challenging problem, and methods for improvement are not straightforward. This book is intended to present the fundamentals of the generation and transmission mechanisms of the tire/road noise in vehicle suspension and road system, and to summarize the state-of-the-art knowledge of the tire/road noise research. The book includes chapters to describe:

• The tire/road noise generation mechanisms

• The tire/road noise measurement and evaluation methods

• Transfer path analysis and control of structure-borne tire/road noise

• Transfer path analysis and control of airborne tire/road noise

• Current technologies and analysis methods used to develop the reduced interior tire/road noise

• Pass-by tire/road noise and traffic regulation

The authors include specialist engineers from major automotive manufacturers and tire component suppliers and researchers from universities. An additional aim of this book is to improve automotive engineering education and to bridge the gap between the automotive industry and universities. The uniqueness of this book is to study the tire/road noise in the system of road, tire, and vehicle as a whole which is different from other books related to this topic. This book only covers the interior and exterior tire/road noise study under the dry road conditions.

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 Lp=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 vehicles and regulations/requirements/expectations will shape the future of the tire/automobile industry.

References

1. Crocker MJ. (e.d.) Introduction chapter in the book Noise Control New York: Van Nostrand Reinhold Co. Inc.; 1984.

2. Sandberg U, Ejsmont JA. Tyre/road noise reference book Kisa, Sweden; Harg, Sweden: INFORMEX; 2002; ISBN 9789163126109, 9163126109.

3. Luetgebrune H. Reifengeräusche - Fahrzeuggeräusche. Kautschuk und Gummi. 1955;4:91–96.

4. Namba S. Noise—quantity and quality. In: Proceedings of inter-Noise 94, Yokohama, Japan; 1994. p. 3–22.

5. Quiet Pavement project underway and news. Arizona Department of Transportation. www.quietroads.com [accessed July 2004].

6. ANSI S1.18. Template method for ground impedance. Acoustical Society of America.

7. Samuels S. The generation of tyre/road noise. ISSN 0518-0728; 1982.

8. Sandberg U. Tire/road noise-myths and realities. In: Proceedings of the 2001 international congress and exhibition on noise control engineering. The Netherlands: The Hague; 2001.

Chapter 2

Tire/road noise separation: tread pattern noise and road texture noise

Tan Li¹, ²,    ¹1Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA, United States,    ²2Maxxis Technology Center, Suwanee, GA, United States

Abstract

Tire/road noise is caused by the interaction between the tire and the road surface. Both tread pattern and road texture excite the tire, causing vibration and air displacement. Close proximity (CPX) method is used to measure the near-field tire/road noise. An optical sensor (tachometer) is also installed to record the once-per-revolution signal of the tire, which is used to perform the order tracking analysis in order to break down the tire noise into the tread pattern and nontread pattern noise components (the latter mainly from pavement excitation). This technique can also be expanded to lab drum test applications where the noise can be separated into tread pattern noise, roadwheel (drum) noise, and turbulence noise components.

Keywords

Tire/road noise; noise separation; tread pattern noise; road texture noise; lab drum surface

2.1 Introduction

Tire/road noise is also known as tire–road interaction noise, tire–pavement interaction noise (TPIN), tire–pavement noise, or tire noise, which is defined as the noise emitted from a rolling tire as a result of the interaction between the tire and the road surface [1]. However, few literatures have reported the mechanisms about this interaction, or the individual contributions from tread pattern and road texture [2,3]. In this chapter, case studies will be demonstrated to reveal the tire–pavement interaction mechanisms.

2.2 Close proximity measurement

In this section, the experimental setup for tire noise data collection is introduced, including test tires, test pavement, test equipment, and test conditions [4,5].

The 37 tires tested are listed in Table 2.1. Their tread pattern pictures are shown in Fig. 2.1 where the red arrow indicates the rotation direction for directional tires in the test. All the tires are tubeless radial tires. Most of the tires are passenger car tires, including all-season tires, winter/snow tires. Tire 42 is for light truck (LT); Tire 53 is for trailer only. Some tires are just for lab purpose but not for sale (Tires 39 and 49). Some tires have the same size and aspect ratio (e.g., Tires 1–19 of 215/60R16) but different tread patterns. Tire 20 is the Standard Reference Test Tire (SRTT). Tires 19, 25, 27, and 29 are the same tire for repeatability evaluation. Tires 12, 24, and 26 are the same tire but in different rotation directions. Tire 43 has long and narrow tread blocks instead of square blocks commonly seen in the other tires. Tire 57 has the same tread pattern as Tire 13 but different tire size and tread depth. It is also noted that Tires 1–30 are of the same size (215/60R16), except Tires 20–23 of 225/60R16 that is very similar size to the former. Tires 31–60 have various sizes.

Table 2.1

Figure 2.1 Tread patterns of the test tires (arrow indicates rotation direction).

The number of pitches, as shown in Table 2.1, is the total number of tread elements (or usually tread blocks) around the full tire circumference. The number of plies in the tread band and the sidewall differs for different tires, indicating that the structure of the tires varies. However, the number of plies is shown to be not very different for the tires tested, thus it is not of interest in this study. The tread rubber hardness was the average of several measurements and it is generally accepted that the tolerance for rubber hardness measurements is ±2 Shore A. Most of the tires are pretty new and well stored in the lab, and the rubber hardness is generally in the range between 60 and 70 Shore A. Some tires, especially the bigger tires, are very old (over 10 years) and the rubber hardness is usually over 70 Shore A due to the age hardening effect.

The test pavement is U.S. Route 460 near Virginia Tech (between Toms Creek Rd. and North Main St. with one-way distance of around 1.3 mile), as shown in Fig. 2.2. It is a nonporous asphalt pavement that is commonly seen in USA. Both eastbound section and westbound section were tested, but only results on eastbound section will be discussed; the results on westbound section show the same trends.

Figure 2.2 Test pavement. From Google Street View.

The testing vehicle used for testing depends on the tire size, to be more specific, the tire outer diameter. The 10 different tire sizes tested are shown in Table 2.2. For the smaller tires with outer diameter smaller than 700 mm, a 2012 Chevrolet Impala LT (front-wheel drive) was used, as shown in Fig. 2.3 (left). For larger tires, a 2017 Chevrolet Tahoe LT was used (all-wheel drive), as shown in Fig. 2.3 (right).

Table 2.2

Figure 2.3 Test vehicles (left: Chevy Impala; right: Chevy Tahoe).

The equipment used for collecting noise data was an on-board sound intensity (OBSI) system based on standard AASHTO TP-76 [6]. The setup of the OBSI system is shown in Fig. 2.4. The system was installed at the rear right tire with a camber angle close to zero. The conventional OBSI system has two sound intensity probes, one at the leading edge of the tire–road contact patch, the other at the trailing edge. The distance between the two probes is 210 mm (8.25 in.); the distance between the probes and the tire sidewall is 114 mm (4.5 in.); the distance between the probes and the ground is 89 mm (3.5 in.). Each probe consists of two microphones to record the sound pressure. The sound intensity along the direction of the two microphones (away from the tire) is then calculated. Therefore a typical OBSI has four microphones: leading inboard (Mic 1), leading outboard (Mic 2), trailing inboard (Mic 3), and trailing outboard (Mic 4). In this chapter, only the data from Mic 1 are used. To that purpose, the OBSI system can be substituted with a close proximity (CPX) system [7]. The present OBSI system also has an optical sensor (tachometer) installed, as shown in Fig. 2.4. The optical sensor radiates a beam onto the surface of the black disk rotating with the tire, and once the beam encounters the retroreflective tape and gets reflected to the optical sensor, the optical sensor generates a pulse. Therefore a pulse signal is recorded at the exact time the tire completes one revolution. The optical signal (once-per-revolution signal) can be used to accurately calculate vehicle speed, acceleration, as well as used for the order tracking analysis, which will be discussed later. The microphone and optical signals were recorded simultaneously at 25.6 kHz.

Figure 2.4 On-board sound intensity (OBSI) with optical sensor installed on the test vehicle.

For each tire, the noise data were collected under five different vehicle speeds, that is, 72, 80, 89, 97, and 105 km/h (45, 50, 55, 60, and 65 mph). In addition, an acceleration test was also conducted where the vehicle accelerated from 72 to 105 km/h (45–65 mph) within 10 seconds. The inflation pressure was set to 221 kPa (32 psi) for the tires on Impala, and to 276 kPa (40 psi) for tires on Tahoe. The ambient temperature range during the test days was 37°F–86°F (3°C–30°C). For repeatability evaluation, Tire 19 was tested in multiple test sets as indicated by Tires 25, 27, and 29; very good repeatability was shown (error <1 dB), indicating the temperature within the normal range does not have much influence on the near-field tire/road noise.

2.3 Tire/road noise separation

2.3.1 Two noise components

The unweighted sound pressure level spectrogram (dB) for Tire 12 during the acceleration test from 72 to 105 km/h (45–65 mph) within 10 seconds is shown in Fig. 2.5. This figure is used to illustrate that there exist two main noise components in the dominant part of the spectrum, that is, 600–1200 Hz. The first component is clearly associated with the vehicle speed or tire speed with the center band frequency going from 700 to 1000 Hz as the vehicle speed increases from 45 to 65 mph. The second component is independent of the vehicle speed (or tire rotation) with the spectral content encompassed always within the fixed frequency range between 600 and