
Principles of Analog Electronics
54
Mechanical waves are often called audio waves, but this expression is inappro-
priate since audio waves are only a subset of mechanical waves. Audio waves are
those within the frequency range audible to humans. Mechanical waves that have
a frequency lower than the audible range are named infrasonic and those that are
a higher frequency are named ultrasonic.
The propagation speed of a mechanical wave varies according to the material in
which it propagates. For example, in air it has a speed of about 340 m/s = (1224 km/h),
in water about 1480 m/s, in soil about 3000 m/s, in steel around 5050 m/s,
andsoon.
Two ...