Beats:A throbbing variation in the loudness of sound caused by interference when two tones of slightly different frequencies are sounded together
Compression: In mechanics, the act of squeezing material and reducing its volume. In sound, a pulse of compressed air; opposite of rarefaction.
Forced Vibration: The vibration of an object that is nearby. The sounding board in a musical instrument amplifies the sound through forced vibration.
Infrasonic: Term applied to sound pitch too low to be heard by the human ear, that is, below 20 hertz.
Natural Frequency: A frequency at which an elastic object, once energized, will vibrate. Minimum energy is required to continue vibration at that frequency. Also called resonant frequency.
Pitch: Term that refers to how high or low sound frequencies appear to be.
Rarefaction: A disturbance in air in which the pressure is lowered. Opposite of compression
Resonance:A phenomenon that occurs when the frequency of forced vibrations on an object matches the object's natural frequency, and a dramatic increase in the amplitude results
Ultrasonic: Term applied to sound frequencies about 20,000 hertz, the normal upper limit of human hearing.