Human ears can hear sound waves that
vibrate in the range from about 20 times a
second (a deep rumbling noise) to about
20,000 times a second (a high-pitched
whistling). (Children can generally hear higher-
pitched sounds than their parents, because
our ability to hear high frequencies gets worse
as we get older.) Speaking more scientifically,
we could say that the sounds we can
perceive have a frequency ranging from 20–
20,000 hertz (Hz). A hertz is a measurement
of how often something vibrates and 1 Hz is
equal to one vibration each second. The
human voice makes sounds ranging from a
few hundred hertz to a few thousand hertz.
i just asked if ultrasound(<20000 Hz) travels faster than audible sound(20Hz-20000Hz)