Page 767 - Automotive Engineering Powertrain Chassis System and Vehicle Body

CHAP TER 2 2. 1 Exterior noise: Assessment and control

(a) 70
AVL Boost calculated
Estimated
60

50
Cylinder pressure (bar) 40

30

20

10

0
0 100 200 300 400 500 600 700 800
Crankshaft angle

(b) 3000
AVL Boost calculated
Estimated
2500
Cylinder gas temperature (K) 2000

1500

1000

500

0
0 100 200 300 400 500 600 700 800
Crankshaft angle
Fig. 22.1-43 Estimates of in-cylinder gas pressure and temperature made using simplified assumptions detailed in Section 22.1.3.14.2.
Comparison is made with the results obtained from a full engine simulation of a 2.0-litre gasoline engine at 5000 rev min 1 using
AVL Boost

Comparisons made between noise measurements near The tonal tyre noise originates from regularities in the
to and far from a rotating tyre suggest that (reported in tyre construction. The random tyre noise originates first
Nilsson (1976)): by radial excitation due to roughness in the road but also
most of the noise originates near to the contact patch; from random tangential movements of the tread pattern
(Nilsson, 1976).
the sound intensity is greatest at the entrance and
exit surfaces of the contact patch; Tonal tyre noise is more speed-dependent than
random tyre noise. Random tyre noise is strongly af-
the exit of the contact patch is important for tonal
fected by the characteristics of the road surface. A simple
components of tyre noise;
empirical relationship between noise levels at 7.5 m and
the tyre sidewall is not a significant radiator of sound.
the tyre noise caused by coasting vehicles is presented in
As a result of the work described above, subsequent in- (Nilsson, 1976). Therefore,
vestigations have concentrated on measuring vibration
and noise levels within the tread of the tyre (Jennewein n
and Bergmann, 1985). L A ¼ C þ 10 log ðV ÞdB (22.1.95)
10

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