period (n.)

A term derived from the study of the physics of sound, and used in ACOUSTIC PHONETICS, referring to the time it takes for a CYCLE of pressure variation in a sound wave to repeat itself. The shorter the period, the more cycles there will be in a given unit of time, and thus the higher the FREQUENCY. Waveforms which show a repeating pattern of vibration are periodic waves; those which do not are aperiodic. Speech makes use of both types of waveform: VOWEL sounds have periodic waveforms; FRICATIVES, for example, involve aperiodic waveforms.