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Design of Car Cabin Noise Cancellation
Ong Sin Yee1, ‘Abdurrahman Suratman2, Nurul Shafikah Mohd Zain3, Mohamud Mire4
SET 4722, Section 1, Group No. 4
Basic Microwave Laboratory, Faculty of Electrical Engineering
Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia
Abstract— According to the increase of long time and distance
driving, noise reduction in vehicle cabin becomes a critical
problem for comfort improvement. The common purpose of
active noise control systems is to reduce acoustical noise in an
environment. This paper gives a brief description of designing a
cabin noise cancellation system and how this technology is
adopted in automotive. The information and research data of the
cabin noise cancellation systems was found by searching the
published papers from vehicle companies and research
authorities. The results of this investigation demonstrate that
cabin noise cancellation systems are capable of providing
significant noise reduction of car to improve the comfort ability
of the cabin.
Keywords— Car noise, car cabin noise cancellation, design cabin
noise cancellation, reduce car noise, engine car noise.
Cabin noise cancellation, also known as active noise
control (ANC), is a method for reducing unwanted sound by
the addition of a second sound specifically designed to cancel
the first. Sound is a pressure wave. A noise-cancellation
speaker emits a sound wave with the same amplitude but with
inverted phase to the original sound. The waves combine to
form a new wave, in a process called interference, and
effectively cancel each other out which is called phase
cancellation, as shown in Fig. 1 .
Fig. 2 The sources of noise associated with a car
Two basic control principles are used widely, that is
feedback and feedforward noise cancellation. Feedforward
noise cancellation uses a signal from a microphone located in
the vicinity of the noise source, and the system filters this
sound to produce the anti-noise, as shown Fig. 3 .
Obviously, the forward filter needs to be designed so that the
sound from the loudspeaker cancels the direct sound from the
source at the location of the listener.
Fig. 3 Feedforward noise cancellations
Fig. 1 The mechanism of active noise control
There are many sources of noise associated with a car, as
shown in Fig. 2. They can be divided into narrowband
harmonic and broadband random noise. Narrowband noise
sources include the engine, drive train, air intake, exhaust and
auxiliary systems such as the radiator fan. Broadband noise is
caused by road tyre interaction and aerodynamic wind noise
The second noise control technique, feedback control, uses
control theory to achieve attenuation of the sound level at the
location of a probe microphone by means of a linear feedback
loop with a large negative gain, as shown in Fig. 4 . This
causes the loudspeaker membrane position to regulate the
sound pressure towards a silence level. The disadvantage is
that the feedback loop can become unstable, and that the
feedback loop amplifies microphone probe noise. In practice,
feedback controllers can attenuate noise in a limited frequency
band, and the amount of attenuation is limited by gain margins
for ensuring stability of the system.
pressure level for human ear is 20 µPa. dB of SPL is defined
SPL= 20 log
Fig. 4 Feedback noise cancellations system is essentially a loop with-ideallylarge negative gain
The noise analysis of the passenger car can be divided into
engine induced noise analysis and road induced noise analysis
transmitted by tire and chassis system. In this paper, we will
focus onto the fundamental source of narrowband noise in a
car which is the engine noise.
The engine is the main contributor of narrow band noise in
a car. The engine RPM gives rise to discrete harmonics which
in this context are called engine orders. In a typical setup the
aim is to reduce certain engine orders reduce or to give a more
pleasant sound. The most suitable processing algorithm is a
feedforward structure, and since the engine RPM comes as a
tachometer signal, the reference signal can be synthesized
from the tachometer data as a pure sinusoidal with the
frequency of the engine order to be controlled.
Most vehicles with an internal combustion engine utilize
materials and passenger compartment designs intended to
isolate the vehicle occupants from engine noise. Sound
deadening materials can be heavy and expensive though,
providing an incentive to find other ways of reducing cabin
noise. Using a series of small microphones and speakers
inside the cabin, the system is designed to remove tyre, wind
and engine noise via anti-noise.
A few vehicles employ systems that actively generate an
"anti-noise" signal inside the cabin using one or more
strategically placed speakers driven by a microprocessor.
These systems monitor the noise inside the vehicle using
microphones and attempt to cancel the noise by generating an
identical signal that is 180 degrees out-of-phase with the
detected signal. Fig. 5 shows the basic structure diagram of
active noise control system for attenuating engine noise .
Where Po=2x10-5Pa. The second parameter is sound
intensity level (SL) . Sound intensity level is rate of energy
flow across a unit area. The measure of the ratio of the two
sound intensities are
SL=10 log dB
Where Io=1x10-12 watts/meter2. The last parameter used to
asses the sound exposure is sound power level (SWL) . It is
use to measure the sound power emitted by a source in all
directions. The SPL can be expressed as
II. DESIGN OF CABIN NOISE CANCELLATION
The active noise cancellation was design in car cabins to
eliminate the unwanted noise . The microphones were used
to capture low end drivetrain frequencies that entering the car
and send a signal to the noise to the network processing to
predict the sound level. The predicted signal is taken as the
input reference signal of the control module system.
The reference signal that come out from the module is drive
to the speaker. Then, the secondary sound is produced which
is nearly equal to the noise signal captured by the
microphones (primary sound). The sound wave from the
speaker meets the primary sound source and cancelling each
In this case, microphones act as a sensor and speaker as
actuator. Active noise control system structure is shown in Fig.
Fig. 6 Active noise cancellation in Ford Fusion Hybrid
Fig. 5 Active noise control system for attenuating engine noise
There are three parameter which are generally used to
assses sound exposure to humans. One of the parameter is
sound pressure level (SPL) expressed in µPa . Audible
According to the theory of active noise cancellation (ANC),
the analysis of the noise control system structure  shown in
Fig. 7. The reference signal is obtained by using engine
vibration acceleration to predict the noise in the car.
Moreover, the low-frequency noise in a car mainly comes
from vibration of the body panels. Three vibration
acceleration signals, which come from the engine, the floor
vibration and the roof panel are collected. Then, by using a
network processing the sound pressure level is predicted and
called reference signal.
The reference signal which comes from the network
processing is modulated and amplified through the power
amplifier. Then, the secondary sound source produced the
sound wave from the speaker and will cancel the noise.
Thus, in the system, engine, roof and the floor are the input
acceleration signals and the speaker is taken as the output.
The data is divided into three categories that are small cars
have CC less than 1000; medium cars have CC between 1000
to 2000 and large cars have CC greater than 2000. The data of
CC, number of cylinder and torque is gotten from the
catalogue for each type of car, as shown in Table 1. A poundfoot (lb·ft) is a unit of torque. One pound-foot is the torque
created by one pound force acting at a perpendicular distance
of one foot from a pivot point .
THE CAR SPECIFICATIONS BASED ON CATEGORY OF CAR
Type of Car
Toyota Mark X
BMW 7Series740i Sedan
Fig. 7 Schematic diagram of active noise control system in car cabins. 1engine vibration acceleration sensor, 2-floor vibration acceleration sensor, 3roof vibration acceleration sensor, 4-error sensors, 5-secondary sound source,
This research paper is about designing of car cabin noise
cancellation, In order to design an engine for a particular
application, it is helpful to determine a various terms such as
horsepower, torque, rpm and cubic centimetres (cc). The
terms horsepower torque, and rpm are used in engineering to
design transmission shafts as well as. When designing a
transmission shaft one must consider the power (watts or
horsepower), and speed of rotation (rpm or frequency) to
choose the proper material so that the maximum shearing
stress allowable will not be exceeded. When speaking of
automobiles torque is defined as a force around a given point,
applied at a radius from that point. Horsepower (hp) is the
name of several units of measurement of power, the rate at
which work is done. A revolution per minute (rpm) is a
measure of the frequency of a rotation. It annotates the
number of turns completed in one minute around a fixed axis.
It is also used as a measure of rotational speed of a mechanical
component. A cylinder is the power unit of an engine; it’s the
chamber where the gasoline is burned and turned into power
This is the simplest set of equations that use in order to find
horsepower, torque, rpm produced by an engine. As folows:
Where f is frequency, Z is number of cylinder and N is
value of RPM .
𝐻𝑜𝑟𝑠𝑒𝑝𝑜𝑤𝑒𝑟 (ℎ𝑝) =
𝑇𝑜𝑟𝑞𝑢𝑒 𝑥 𝑅𝑃𝑀
Where RPM is revolution per minute .
Size of Cubic
No. of Torque
A. Relationship between Revolution per Minute (RPM) with
The value of RPM and number of cylinder is used to find
the value of noise frequency with equation (4). The value of
noise frequency is recorded in Table 2.
THE VALUE OF NUMBER OF CYLINDER, RPM AND NOISE FREQUENCY FOR
EACH TYPE OF CAR
Type of Car
(1000<CC<20 Toyota Vios
Toyota Mark X
BMW 7Series740i Sedan
THE VALUE OF SOUND POWER LEVEL (SWL) AND NOISE FREQUENCY BASED
ON TYPE OF CAR
Fig. 8 The graph of noise frequency (Hz) versus RPM
The Fig. 8 shows the graph of noise frequency versus RPM
based on the value of noise frequency calculated and value of
RPM from Table 2. From the graph, if the value of RPM
increases than the noise frequency increases. The increases of
RPM mean the increases speed of the car. The speed of car
increases will affect the noise frequency to increases.
B. Relationship between Sizes of Car Engine with Noise
Fig. 9 The graph of noise frequency (Hz) versus number of cylinder
The Fig. 9 shows the graph of noise frequency versus the
number of cylinder based on the value of noise frequency
calculated, value of RPM is fixed at 3000 and the number of
cylinder from Table 2. The number of cylinder increases
means the size of car engine increases. From the graph, if the
size of the engine increases than the noise frequency increases.
C. Relationship between Sound Power Level (SWL) with
The first step to calculated sound pressure level is based on
the data of torque and RPM from Table 1 and use it to
calculate the value of horsepower using equation (5). Next,
convert horsepower to watts using equation (6) is the most
common conversion factor, especially for mechanical power
1ℎ𝑝 = 746 𝑊𝑎𝑡𝑡𝑠
The value of sound power level is calculated using equation
(3) and the value of SWL is compared to noise frequency
based on the value of RPM, as shown in Table 3.
Level (SWL) (dB)