Key Terms

beat frequency

frequency of beats produced by sound waves that differ in frequency

beats

constructive and destructive interference of two or more frequencies of sound

bow wake

v-shaped disturbance created when the wave source moves faster than the wave propagation speed

Doppler effect

alteration in the observed frequency of a sound due to motion of either the source or the observer

Doppler shift

actual change in frequency due to relative motion of source and observer

fundamental

the lowest-frequency resonance

harmonics

the term used to refer collectively to the fundamental and its overtones

hearing

perception of sound

loudness

perception of sound intensity

notes

basic unit of music with specific names, combined to generate tunes

overtones

all resonant frequencies higher than the fundamental

phon

numerical unit of loudness

pitch

perception of the frequency of a sound

shock wave

wave front that is produced when a sound source moves faster than the speed of sound

sonic boom

loud noise that occurs as a shock wave as it sweeps along the ground

sound

traveling pressure wave that may be periodic; the wave can be modeled as a pressure wave or as an oscillation of molecules

sound intensity level

unitless quantity telling you the level of the sound relative to a fixed standard

sound pressure level

ratio of the pressure amplitude to a reference pressure

timbre

number and relative intensity of multiple sound frequencies

transducer

device that converts energy of a signal into measurable energy form, for example, a microphone converts sound waves into an electrical signal