In general terms, "frequency" is the rate (how often) at which something repeats. In acoustic terms, it is the rate at which sound waves repeat over time. The greater the number of repeats, the higher the frequency. And the higher the frequency, the higher the pitch of the tone that is produced. Consequently, high- frequency waves are very short, and low frequency waves are very long (up to fifteen feet). In audio the indication of how many cycles of a repetitive waveform occurs during one second. A waveform which repeats once per each second has a frequency of 1Hz (Hertz.) Frequency also references to human hearing as pitch.