Transient

A sudden and brief fluctuation in a sound. The sound of a crack on a record, for example.

See: Click, Envelope, Transient Response, Waveform. Compare: Grain, Impact Sound, Pulse.

In the initial part of any sound there occur a number of these fluctuations, for instance, the moment a violinist puts the bow to the string or the trumpeter tongues the notes. These are called onset transients and are important in identifying the sound source and its spatial location and timbre. If these are spliced out of a recording of the sound, it will easily be confused with other sounds.

See diagram under Fourier analysis and Fourier synthesis.

A linguistic example of transients is the initial Consonant in words such as: till, pill, kill, bill. The lack of intelligibility of speech in spaces with long reverberation times (see diffuse sound field) is mainly due to the masking of such transients by reflected sound. Since onset transients often include high frequency components, loss of hearing sensitivity in this range (presbycusis) results in decreased ability to distinguish between similar sounds or syllables. Compare: Residue.

A transient sound is one whose average properties change in time such as a passing car, a sonic boom, or an aircraft flying over.

Compare: Internal Dynamics, Stationary Sound.