Page 676 - Automotive Engineering Powertrain Chassis System and Vehicle Body

21.1
Chapter 21.1

Interior noise: Assessment

and control

Matthew Harrison

21.1.1 Subjective and objective noise sources) and then producing radiated sound inside
methods of assessment the compartment. This process is illustrated in Fig. 21.1-1.
The interaction with the structure can be either as:
21.1.1.1 Background An airborne noise path – airborne noise from outside
the passenger compartment leaking in to cause air-
Vehicle interior noise is a combination of: borne noise inside.
A structure-borne noise path – vibration from out-
engine noise;
side causing the surfaces of the passenger compart-
road noise;
ment to vibrate and radiate noise.
intake noise;
Direct airborne noise paths are found where there is
exhaust noise; a lack of sealing between the interior and the exterior
aerodynamic noise; environments (around door seals, grommets in the
noise from components and ancillaries; bulkhead, etc.). Indirect airborne noise paths are found
brake noise; when airborne noise outside impinges on the surfaces of
squeaks, rattles and ‘tizzes’. the passenger compartment, causing them to vibrate and
Apart from squeaks, rattles and tizzes that occur inside radiate noise inside.
the passenger compartment, noise or vibration usually The interaction between the noise source and the
originates from outside, interacting with the vehicle structure has a filtering effect on the final interior noise
structure in some way (and possibly hence with other level (see Fig. 21.1-1). For instance, in the case of indirect

Interaction with vehicle Sound
Noise source 1
structure – filter effect radiation
Acoustics
of the
Interaction with vehicle Sound
Noise source 2 interior – Interior noise
structure – filter effect radiation
filter
effect
Interaction with vehicle Sound
Noise source n
structure – filter effect radiation
Fig. 21.1-1 Schematic showing the origin of interior noise.
Vehicle Refinement; ISBN: 9780750661294
Copyright Ó 2004 Matthew Harrison. All rights of reproduction, in any form, reserved.