Noise and vibration are of concern with many mechanical systems,
including industrial machines, home appliances, vehicles,
and buildings.1-3 Noise and vibration can also be used as the
source of signals for machinery diagnostics and health monitoring,
although this topic will not be discussed here.4,5 Once noise and
vibration sources have been identified, the noise and vibration of
machinery can be reduced by the use of vibration isolation, barriers,
sound-absorbing materials, machine enclosures or by cabin enclosures
used to protect passengers in the case of aircraft or vehicles.6,7
Sound-absorbing materials should always be used in conjunction
with barriers and inside enclosures to improve their effectiveness.8
Sound-absorbing materials have been used increasingly in the
construction of aircraft, spacecraft and ships because of their low
weight and effectiveness when used correctly. This trend is driven
by demands for higher load capacity and reduced fuel consumption
for cars, trucks and aerospace structures. The optimum design
of vibro-acoustical systems can be achieved through a variety of
methods including statistical energy analysis (SEA).9