tire noise reduction

STUDY AND ANALYSIS OF TIRE NOISE

A PROJECT REPORT

Submitted by

in partial fulfillment for the award of the degree

of

BACHELOR OF ENGINEERING

in

MECHANICAL ENGINEERING

VEL TECH, AVADI, CHENNAI

ANNA UNIVERSITY: CHENNAI 600 025

APRIL 2016

SENTHIL NAYAGAM D (Reg.NO:112912114094)

VENUGOPALAN M (Reg.NO:112912114106)

VIGNESHWARAN K (Reg.NO:112912114111)

ANNA UNIVERSITY : CHENNAI 600 025

BONAFIDE CERTIFICATE

Certificate that this project report “STUDY AND ANALYSIS OF TIRE NOISE” is

the bonafide work of “VIGNESHWARAN K (112912114111), VENUGOPALAN

M (112912114106), SENTHlL NAYAGAM D (112912114094)” who carried out the

project work under my supervision.

SIGNATURE SIGNATURE

Mr.R.PALANISAMY, M.E, Mr. J.ARULMANI, M.E,

HEAD OF THE DEPARTMENT ASSISTANT PROFESSOR,

Department Of Mechanical Eng. Department Of Mechanical Eng.,

VEL TECH Engineering College VEL TECH Engineering College

Avadi-62 Avadi-62

INTERNAL EXAMINER EXTERNAL EXAMINER

Submitted for the Viva-Voce held on /04/2016 at Veltech

ACKNOWLEDGEMENT

We would express our beloved chairman SHRI COL.Dr.R.RANGARAJAN

VEL TECH ENGINEERING COLLEGE, AVADI, 600062 for arranging this project.

We would also express our sincere thanks to our principal

Dr.B.NAGALINGESWARA RAJU and head of the department

Mr.R.PALANISAMY for having made for guidance and counseling throughout this

project work.

We would like to express our sincere gratitude to Mr. M.JAGAN MOHAN RAO

Mr.NAGASURESH.I, Mr. S. NANDAKUMAR & Mr. P. JEBA SINGH of NVH

Attribute Engineering division, Ashok Leyland Technical Centre,

Velivoyalchavadi for their valuable guidance and facilities without which this project

would not have been possible

We also thank our Internal guide Mr. J.ARULMANI for his inspiration, invaluable

guidance and constant which helped us to design this project

ABSTRACT

Automotive industries perform NVH test on vehicles in the end user environment to

reduce failures and warranty costs in the end user hands. Noise and vibration produced

in the vehicle are equally important from a customer point of view. Different vehicle

manufactures follow different tire noise measurement techniques. From the

observation it is found that many of benchmark companies using Pass by noise and

other methods for measuring tire noise.

This Report describes the mechanism of generating tire noise, which contributes very

much to the vehicle exterior noise, by dividing the factors of the tire noise into

exciting force, vibration characteristics and acoustic radiation characteristics. In

addition, it shows the effectiveness of suppressing the distinctive tread vibration

mode, which is the main mode of vibration radiating noise of around 1 kHz with a

high sound pressure level in radial tires for commercial vehicles.

The tire testing was done for various speed levels and pressure levels and

the noise was captured with the help of a sound level meter (SLM) in the high speed

testing tracks and the different conditions of testing was conducted and the readings

were converted into graph by processing the values taken from the microphone and

SLM, and converting them into graphs by using LMS software. The result of the tests

are presented in the following report.

TABLE OF CONTENTS

CHAPTERS TITLE PAGE NO.

ACKNOWLEDGEMENT iii

ABSTRACT iv

TABLE OF CONTENTS v

LIST OF FIGURES viii

1. INTRODUCTION

1.1. DESCTRIPTION 1

1.2. SOUND 2

1.3. GENERATION OF SOUND 2

1.4. FREQUENCY 2

1.5. THE SPEED OF SOUND IN DIFFERENT 2

MEDIUM

1.6. SOUND PRESSURE LEVEL 3

1.7. OCTAVE 3

1.8. OCTAVE ANALYSIS 5

1.9. OCTAVE BAND 5

1.10. 1/3RD

OCTAVE ANALYSIS 5

1.11. SOURCES OF ENVIRONMENTAL NOISE 6

1.12. MEASUREMENT CHAIN GENERAL 7

ANALYSIS

1.13. BASICS OF VIBRATION 7

1.14. UNITS OF VIBRATION 8

1.15. ELEMENTS OF VIBRATION 8

1.16. VIBRATION DISCRIPTORS 9

1.16.1. AMPLITUDE 9

1.16.2. PERIOD AND FREQUENCY 9

1.17. PHASE AND ITS IMPORTANCE 10

2. INTRODUCTION OF TIRES

2.1. TERMINOLOGY OF TIRES 12

2.2. TYPES OF TIRES 13

2.3. INSTRUMENTS USED FOR TESTING 16

2.3.1. MICROPHONE 16

3. LITREATURE SURVEY 17

4. 4.1 METHODOLOGY 20

4.2. LOCATION OF MICROPHONE 20

4.3. COAST DOWN NEAR SOURCE METHOD 22

4.4. COAST DOWN NEAR SOURCE METHOD 25

FOR SMALLER TIRE

4.5. TEST RESULT 26

4.6. FOR DIFFERENT TIRE PRESSURE LEVELS 28

AT CONSTANT SPEED

4.7. FOR DIFFERENT SPEEDS AT CONSTATNT 29

PRESSURE LEVELS

4.8. NOISE LEVEL FOR DIFFERENT TIRE 29

SIZES

5. PHOTOGRAPHS 30

6. REFERENCES 35

LIST OF FIGURES

S.NO TITLE PAGE NO

FIG 1.1 Generation of sound waves 2

FIG 1.2 1/3rd

Octave 6

FIG 1.3 Noise level 7

FIG 1.4 Measurement chain 8

FIG 1.5 Elements of vibration 9

FIG 1.6 Amplitude 11

FIG 2.1 Tire terminology 13

FIG 2.2 Types of tires 14

FIG 2.3 Tire resonance 13

FIG 2.4 Microphone 18

FIG 4.1 Analysis for bigger tire 19

FIG 4.2 Location of microphone 25

FIG 4.3 Frequency vs dB for 60kmph 26



FIG 4.6 Frequency vs dB for 60 psi 27




FIG 4.10 Frequency vs dB for different tire size 29

1

CHAPTER 1

INTRODUCTION Vehicle manufacturers work with noise and vibration control to fulfill

legislation demands and to meet customer requirements. The exterior

noise control work is mainly motivated by legislation demands while

interior noise and vibration control work is motivated by driver and

passenger noise and vibration comfort requirements. The motivation for

reducing traffic noise is that it is the most important environmental noise

source in India and in the rest of the world.

1.1 DESCRPTION Noise: It is unwanted sound. The sound is propagating type of energy

traveling through a medium with particular velocity. Vibration: The vibration is the variation of the displacement of a body

with respect to a specified reference position with time, when

displacement is alternatively greater or smaller than reference. Harshness : Vibration perceived tactually and audibly in the frequency

range of 15 Hz to 300 Hz.

2

1.2 Sound:

Physically, a mechanical disturbance propagated as a wave motion in air

and other elastic or mechanical media such as water or steel.

Physiologically, an auditory sensation evoked by this physical

phenomenon. Not all sound waves evoke an auditory

sensation,e.g., ultrasound.

1.3 Generation of sound waves: Sound waves involve a succession of compressions and rarefactions of an elastic

medium such as air characterized by the amplitude of pressure changes, their

frequency, and the velocity of propagation.

Fig 1.1

3

1.4 Frequency:

The number of compressions and rarefactions per unit time in seconds. f = 1/T Unit of frequency is hertz (Hz). Human hearing is sensitive 20-20,000 Hz (the audio frequency range).

1.5 THE SPEED OF SOUND IN DIFFERENT MEDIUM:

In air - 344 m/s (1240 km/h).

In wood - 3,962 m/s (11 times of air)

In steel - 5,029 m/s (15 times of air) 1.6 SOUND PRESSURE LEVEL (SPL): Sound Pressure Level is used as the fundamental measure of

sound(amplitude).Threshold SPL of all "average" person at 1,000 Hz is 20 N/m2

Largest sound pressure perceived without discomfort : SPL in logarithmic scale

varies between 0 to 130

1.7 Octave

• Human Ear cannot differentiate small variations in frequency

Example : We cannot perceived the difference between tone of 1.0kHz and 1.2

kHz

• Octave are the minimum frequency shift necessary for human being to

perceive the difference of tones

Octave bands are standardized starting from 1.25Hz to 20kHz

4

1.8 Octave analysis: When more detailed information about a complex sound is needed, the frequency

range of 20Hz to 20kHz can be split into sections or bands. This is done

electronically within a sound level meter.

These bands usually have a bandwidth of one octave or one third octave. More

advanced instruments may be able to give a narrow band analysis of the noise

data. This may be an FFT (Fast Fourier Transform) or information in 1/12 octaves.

An octave band is a frequency band where the highest frequency is twice the

lowest frequency.

For example, an octave filter with a centre frequency of 1kHz has a lower

frequency of 707Hz and an upper frequency of 1.414kHz. Any frequencies below

and above these limits are rejected. A third octave has a width of 1/3 of that of an

octave band.

1.9 Octave band: An octave band is a frequency band where the highest frequency is twice the

lowest frequency. For example, an octave filter with a centre frequency of 1kHz

has a lower frequency of 707Hz and an upper frequency of 1.414kHz. Any

frequencies below and above these limits are rejected

5

1.10 1/3 OCTAVE ANALYSIS: It is one type of octave analysis which is done for comparing for multiple

components and also for analyzing for modified measurements, for constant RPM

. Here one frequency is compared other frequencies.

Fi1g 1.2

This is one of the example for 1/3 octave analysis graph which has been done for

our project 1.11 SOURCES OF ENVIRONMENTAL NOISE

Industries

Road-traffic

Rail-traffic

Air-traffic

Construction and public works

FIG 1.2

6

Noise prevention and control is important as noise affects us in

Hearing

Ability to communicate

Behavior

Indoor sources (air conditioners, air coolers, fans, radio,television and

other home & office etc

Indiscriminate use of loudspeakers, generator sets and Fire crackers have

given a new dimension to the noise pollution problems in India

Fig 1.3

FIG 1.3

7

1.12 MEASUREMENT CHAIN – GENERAL ANALYSIS

Fig 1.4

1.13 Basics of Vibration:

1.13.1 Definition Basically, vibration is oscillating motion of a particle or body about a fixed

reference point. Such motion may be simple harmonic (sinusoidal) or complex

(non-sinusoidal). It can also occur in various modes - such as bending or

translational modes - and, since the vibration can occur in more than one mode

simultaneously, its analysis can be difficult.

FIG 1.4

8

1.14 Units of vibration The units of vibration depend on the vibrational parameter, as follows: a) acceleration, measured in g or [m/s2] ; b) velocity, measured in [m/s] ; c) displacement, measured in [m].

1.15 ELEMENTS OF VIBRATION: 1. Mass (M) 2. Spring (K) 3. Damper (c) 4. Excitation(X[T])

Fig 1.5

9

The three most important descriptors of Vibration are 1.Amplitude 2.Period and Frequency 3.Phase

1.16 Vibration Descriptors: 1.16.1 Amplitude

Fig 1.6

Fig 1.6

10

Amplitude of Vibration is the Magnitude of Vibration Amplitude is measured and expressed in three ways:

• Displacement (in Microns)

• Velocity (mm/sec)

• Acceleration (m/sec or g)

1.16.2 Period & Frequency

• Frequency expressed in Hertz (CPS)

– f in Hz = RPM / 60

• Cycles per minute (CPM /RPM) – CPS * 60

• Radian per second (Circular frequency) – ω = 2π f

11

1.17 PHASE & ITS IMPORTANCE

• Vibration phase can be simply defined as the moment at which event

occurs.

• The phase relation could be in degrees, time (second) or fraction of a

revolution or cycle

Fig1.7

Fig 1.7

12

CHAPTER 2

INTRODUCTION ABOUT TIRE NOISE Exterior road traffic noise results from the combined contributions from a large

number of different vehicles. Trucks are typically noisiest followed by buses and

motorcycles while cars are the quietest. The contribution of cars to the overall

traffic noise level is however great because of their large numbers (about 80% of

the road traffic). For lower speeds, below 40-50 km/h, engine noise including

exhaust and intake noise dominates for cars. For higher speeds, above 70 km/h,

tyre-road noise dominates the car exterior noise generation. For heavier vehicles

the engine noise is dominant under most conditions. The next to that engine noise

tire noise is dominating so research are going on to reduce the road/tire noise.

2.1 TERMINOLOGY OF TIRES: Air Pressure: The amount of air inside the tire pressing outward on each square

inch of tire, expressed in pounds per square inch (psi) or kilopascals (kPa), the

metric designation for air pressure. Alignment: The state in which all wheels on a vehicle are pointed in the optimum

direction relative to one another. All-Season Tires: Tires that are designed for use on dry and wet pavement and

also provide traction on snow and ice. Cold Inflation: The amount of air pressure in a tire, measured in pressure

kilopascals (kPa) or pounds per square inch (psi), before a tire has built up heat

from driving.

13

Cord: The strands of fabric forming the plies or layers of the tire. Cords may be

made from steel, fiber glass, rayon, nylon, polyester or other fabrics. Contact Patch: The portion of the tread that makes contact with the road. Groove: The space between two adjacent tread ribs; also called tread grooves. Highway Tires: Also called Summer tires; designed for wet- and dry-weather

driving, but not for use on snow and ice. Load Index: An assigned number ranging from 0 to 279 that corresponds to the

load carrying capacity of a tire. Ply: A rubber-coated layer of fabric containing cords that run parallel to each

other, extends from bead to bead and goes between the inner liner and belts or

tread. Pounds per square inch (psi): The imperial unit for air pressure. Radial Ply Tire: A type of tire with plies arranged so cords in the body run at 90

degree angles to the centre line of the tread. Rolling Resistance: The force required to keep a tire moving at a uniform speed.

The lower the rolling resistance, the less energy needed to keep a tire moving. Tread: That portion of a tire that comes into contact with the road. It is

distinguished by the design of its ribs and grooves.

Fig 2.1

14

2.2 Types of tires:

• Summer tires

• Winter tires

• All season tire

• Wet climate tire

• Performance tire

• All terrain tires

• Run flat tires

• Eco

• Tubeless

• Tube

• Radial

Fig 2.2

Fig 2.2

15

TIRE NOISE SOURCE IDENTIFICATION METHODS: TIRE NOISE PREDICTION – INITIAL PROCESS DEVELOPMENT

• Road testing

• Jury evaluation testing

• Regression modal development

• Characterisation of sources and paths

• Component level test development

• Synthesis process development

TIRE NOISE PREDICTION – PROCESS UPDATES

• Evaluation of Additional Tire Designs

• Structure-borne Contributions

FIG 2.3

Tire noise depends upon various factors:

• Tread design

• Cupped design

• Improper inflation

• Failure to rotate

Fig 2.3

16

2.3 Instruments used for Testing: The various instruments used to measure are:

Linear accelerometers

Sound level meter

Microphone

LMS test lab software

3.3.2 Microphone: These microphones are designed for high-level and very high-frequency

measurements and measurements in confined spaces. Being externally polarized, it

must be used with a classical preamplifier. Uses of these microphones Pressure-field microphones should be used for making measurements in small, closed couplers or close to hard, reflective surfaces. Such microphones are optimized to have a flat frequency response in a pressure field. Because of its small size, Type 4138 can also be used for random-incidence measurements at audio frequencies, where its frequency response is less dependent on angle of incidence.

Fig 2.4 Fig 2.4

17

Chapter 3

LITERATURE REVIEW

The area tire noise and vibration is very extensive. While reviewing the

various journals and publications on tire noise testing, three of the journals and

publications were of particular intrest. The first was the A study on the mechanism of

tire/road noise by Keijiro Iwao, Ichiro Yamazaki. This journal describes the

mechanism of generating tire/road noise, which contributes very much to the vehicle

exterior noise, by dividing the factors of the tire/road noise into exciting force,

vibration characteristics and acoustic radiation characteristics. In addition, it shows the

effectiveness of suppressing the distinctive tread vibration mode, which is the main

mode of vibration radiating noise of around 1 kHz with a high sound pressure level in

radial tires for Commercial vehicles.

18

In commercially available tires for passenger cars, tread patterns formed on tread

surfaces for drainage have an unequal pitch arrangement in the circumferential

directionof the tires, as shown in Fig. 2. This aims at dispersing the pattern noise

synchronized to the interval between neighboring patterns, from the pure tone sound,

which is offensive to the ear, into sound of a wide frequency range, which is less

offensive to the ear, by changing the interval between the neighboring patterns as

shown in Fig. 3. For example, under the condition of a car speed of 50 km/h,

the sound synchronized to the first-order component of the pattern having a central

frequency of 500 Hz is dispersed into the frequency range from 400 Hz to 600 Hz, and

the sound synchronized to the second-order component of the pattern is dispersed into

the frequency range from 800 Hz to 1.2 kHz. Consequently, if the frequency

component synchronized to the tread patterns is to be identified, it is

necessary to take a wide frequency range into consideration instead of a single

frequency. In order to investigate the effect of the tread pattern on the tire/road noise,

the noise spectrum of a smoothed tire, whose tread blocks were removed to smooth

the surface, was compared with an original tire under the coasting condition without

driving torque, as shown in Fig. 4. It is found that the sound pressure level depends

upon the roughness of the road surface. In the case of the experiment conducted on a

chassis dynamometer (called C/D hereafter) having a smooth surface, the sound

pressure level of the smoothed tire was lowered remarkably in the frequency range

from 400 Hz to 600 Hz, which seems to correspond to the first-order component of the

tread pattern, and in the frequency range from 800 Hz to 1.25 kHz, which seems to

correspond to the second-order component of the tread pattern. However, in the case

of the experiment conducted on the actual pavement, the sound pressure level rose as

19

a whole in the frequency range having a center frequency of about 1 kHz, compared

with the case on C/D. Furthermore, it is remarkable that the sound pressure level of

the smoothed tire is higher than that of the original tire in the frequency range above

1kHz, contrary to the case on C/D. It is found from these results that the tire/road

noise depends not only upon the exciting force due to the tread pattern and the

roughness of the road surface, but also largely upon the structure of the tire, such as

thickness of the tread blocks.

20

CHAPTER 4

4.1 METHODOLOGY: In this work a Truck of tire size 10R20 and a Bus of tire size of 7.5R16 is taken for study of the

Tire noise.

Coast down near source noise

Test on various pressure level for tires

Test on various speed levels

Test on different sized tires

4.2 Location of microphones:

Microphone placed near rear of the tire (about 8-10cm from the tire)

In the road surface about 1m from the vehicle during pass by

4.3 COAST DOWN NEAR SOURCE METHOD The distance from the microphone positions from the tire is about 0.5m which is

called as near source. That is the microphone is mounted near the mud guard of

the vehicle. Another microphone is kept in the road nearer to tire while it is

passing. And sound is measured.

21

Fig 4.1 Natural frequency of tire is found at 1100Hz for thread surface by doing frequency

response function test (i.e) is done by exciting the tire with the help of hammer.

The next graph tells us about the color map of tire noise by doing coast by method

it is found that the tire noise is recognized only at 0-200Hz (i.e) low frequency.

The last graphs tell us about the 1/3rd

octave analysis of tire tread near source

noise and it is found out that at 2 frequencies that is at 160hz and 1000hz

Fig 4.1

22

COAST DOWN NEAR SOURCE FOR LARGER TIRE

• This method is used to determine the sound that is coming out from the tires

when they are driven at higher speeds.

• In this method microphones are placed at various places in the trucks and

are connected to a measuring device.

• When the truck is driven at a speed of 70 to 80kmph the various sound

coming from the tire are captured in the microphone which is measured

using the measuring software's.

Based on the values obtained a graph is generated to find the peak at which the

noise is high and the processing is concentrated on the particular region

23

Location of microphone

24

FREQUENCY RESPONSE FUNCTION:

Frequency response is the quantitative measure of the output spectrum of a

system or device in response to a stimulus, and is used to characterize the

dynamics of the system. It is a measure of magnitude and phase of the output as

a function of frequency, in comparison to the input.

25

4.4. Coast down near source method for smaller tire:

Next for different tire pressure levels for different speeds the noise level was found out

using

Fig 4.2 Location of microphone

Fig 4.2 – location of microphone

26

4.5 Test results:

At 60kmph

Fig 4.3 Frequency vs dB for 60kmph

At 50kmph


27

At 40 kmph


AT 60psi pressure

Fig 4.6 Frequency vs dB for 60psi pressure

28

At 70psi pressure


At 80psi pressure


29

At 90psi pressure


4.6 FOR DIFFERENT TIRE PRESSURE LEVELS AT

CONSTANT SPEED:

• The graph (fig 4.3- 4.5) implies that at high tire pressure levels the tire noise

is relatively low as compared to low pressure level. This is because increase

in tire pressure level decreases the contact surface between the road and the

tire and side wall stiffness of the tire gets increased.

• If the tire pressure level is low the noise is high. This is due to the increase

in contact surface between road and tire. This increases the air pumping

pressure and noise generated is more.

• At lower frequency for higher pressure level the noise produced is relatively

low.

30

4.7 FOR DIFFERENT SPEEDS AT CONSTANT PRESSURE

LEVEL:

• The graph (Fig 4.6-4.9)implies that, at high speed levels the tire noise is

relatively more compared to low speed. This is because increase in rotation

of tire, causes the air cavity resonance between tread patterns is more and

faster and thus the noise is high.

• For low speed level the rotation of tire is less and the air cavity resonance

between the tread patterns low compared to high speed levels.

4.8 NOISE LEVEL FOR DIFFERENT TIRE SIZES: For Different Tire Sizes the Noise Level Is Calculated and The Graph Is Plotted

Tire Noise with Different Tire size

Fig 4.10

31

Note: Redline indicates 10R20 (i.e larger tire)

Black line indicates 7.5 R 16 (i.e smaller tire)

The result is analyzed that, large sized tire produce more noise than the

small sized tire.

This is because for larger tire size the tread size is larger and the volume

of air entering and leaving between the treads is more and thus it leads to

increase in tire noise

For smaller sized tire the tread size is smaller and the volume of air

entering and leaving between the treads is less and thus the tire noise is less

32

PHOTOGRAPHS: .

35

REFERENCES

1. Alan E.Ducan, Frank C.Su, Walter L. Wolf ‘Understanding NVH basics

2. Per Rasmussen and Svend Gade, Brüel&Kjær, Denmark ‘Tire Noise

Measurement on A moving vehicle’.

3. Jens Slama ‘Evaluation of a new Method for tire/road noise’.

4. Douglas I. Hanson Robert S. James Christopher Ne Smith ’Tire/pavement

noise study’.

5. Keijiro Iwao, Ichiro Yamazaki’ A Study on the mechanism of tire / road

noise’

6. G R Watts, P M Nelson, P G Abbott, R E Stait and C Treleven. ‘Tire/road

noise

Assessment of the existing and proposed tire noise limits.’

tire noise reduction

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