Therefore care must be taken to reduce the vibrating area and/or reduce the vibration velocity.
Reducing the vibrating area can be carried out by separating a large area into small areas, using
a flexible joint. Reduction of the vibration velocity can be carried out by using damping materials
at resonance frequencies and/or blocking the induced forced vibration. A reduction of the
excitation forces and consequently of the vibration velocity response by a factor of two can
provide a possible sound power reduction of up to 6 dB assuming that the other parameters are
kept constant. Typical examples of solid vibration sources are: eccentric loaded rotating
machines, panel and machine cover vibration which can radiate sound like a loudspeaker, and
impact induced resonant free vibration of a surface.