longitudinal wave: a wave in which the individual motion
that makes up the wave is in the same direction as the motion
of the wave (in contrast to a transverse wave in which the individual
motion that makes up the wave is perpendicular to the motion of
the wave).
audible range of frequencies: the range of frequencies
that can be heard by a human ear. Typically, this is about 50
Hz to 20 kHz. As people grow older they tend to loose their ability
to hear higher frequencies so the audible range may decrease to
about 50 Hz to 12 kHz.
infrasonic: frequencies below the audible range
ultrasonic: frequencies above the audible range
supersonic: speeds greater than the speed of sound
speed of sound: for air, about 345 m/s (1240 km/h or 770
m/h) at ordinary room temperature (23C)
loudness: a description of the power carried across an
area by sound; a description of the amplitude of a sound wave
fundamental frequency: the lowest frequency present in
a sound; determines the pitch of the sound
pitch: how low or high a sound is; determined by the fundamental frequency of the sound
harmonics: additional frequencies that are present in a
sound in addition to the fundamental frequency; also called overtones
overtones: additional frequencies that are present in a
sound in addition to the fundamental frequency; also called harmonics
quality: distinctive characteristics that make up an individual
sound; collection of fundamental and harmonics that distinguish
an individual sound
attack: details of how a sound begins
decay: details of how a sound stops
octave: a sound with twice the frequency of another is
one octave higher
equally tempered scale: a scale in which the frequency
of each successive note is 1.06 times greater than the previous
one
beats: the rise and fall in loudness that is heard when
two sounds of nearly the same frequency are heard together
beat frequency: the frequency with which the loudness rises
and falls as two sounds of nearly the same frequency are heard
together; equal to the difference in the frequency of the two
sounds causing the beats
Doppler effect: the change in pitch that is heard due to
a moving sound source or to a moving listener
sonic boom: the loud noise and pressure wave caused by
the buildup of sound waves as an object travels faster than the
speed of sound.
