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 4.4 Frequency vs dB for 50kmph 26
FIG 4.5 Frequency vs dB for 40kmph 27
FIG 4.6 Frequency vs dB for 60 psi 27
FIG 4.7 Frequency vs dB for 70 psi 28
FIG 4.8 Frequency vs dB for 80 psi 28
FIG 4.9 Frequency vs dB for 90 psi 29
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
Fig 4.4 Frequency vs dB for 50kmph
27
At 40 kmph
Fig 4.5 Frequency vs dB for 40kmph
AT 60psi pressure
Fig 4.6 Frequency vs dB for 60psi pressure
28
At 70psi pressure
Fig 4.7 Frequency vs dB for 70psi pressure
At 80psi pressure
Fig 4.8 Frequency vs dB for 80psi pressure
29
At 90psi pressure
Fig 4.9 Frequency vs dB for 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: .
33
34
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.’
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