CS35 2013.04
1.1.5-1 1.1.5-1Noise, Vibration and Harshness
Description and Operation
This chapter briefly introduces the noise and
vibratin generation and how to eliminate it.
Meaning of NVH in Automotive
Engineering
N = Noise - au
dible so
und.
V = Vibration - perceptible vibration .
H = Harshness - audible and perceptible jittering
and
vibratio
n .
Noise Type in Automobile Engi-
neering
Accordinting to sound intensity, the noise in auto-
mobile engineering can be classified as following:
• Slight noise-low thunder, buzz.
•
M
ode
rate no
ise
-rapid
drone.
•
S
tro
ng noise-loud h
o
wlin
g, harsh whistle.
•
Loud ho
wling an
d wh
istle will
h
u
rt the
ears.
Dif
f
erent positions on
vehicle ma
ke noises
in dif-
fere
nt int
ensity:
• Slight noise mostly comes from engine.
• Slight noise alos can be produced on
road, espe
cia
lly
on rough road.
It
is
another type of slight noise, just like
driver ca
n feel the vibra
t
ion o
f
veh
i
cle.
•
S
tro
ng noise (su
c
h as howling and ha
rsh
wh
ist
l
e) is commonly
g
enerat
ed by
airflow or accessories (such as
altern
ators and d
r
iving be
lt
s).
•
C
h
a
tter sound
can
be h
eard whe
n
ve
hicle
runs on tough road. The unstable noise is
usually caused by the shock absorber,
chassis components or loosened
components inside the vehicle.
Sound T
r
ansmitted Through Air
Sound Transmitted Through Object
The sound is transmitted through liquid or solid
(such
as vehicle
body).
The speed (sound velocity) of sound depends on
the object materials. Generally, the transmitting
speed of
sound
in liquid and solid is fast
er than
the transmitting speed in air (about 5 times).
Sound Transmitted Through Air and
Object
CAUTION: The noise transmitting through
air and object is the main concern of the
automotive engineering.
Item Component Description
1-
Sound source (such as
engine)
2 - Sound wave
3
-
Am
plitude
.
.
o
se,
ra
on an
Harshness
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