Transients

Author: N.H. Crowhurst

The word "transient" means something that is passing or changing. Within the strict meaning of the word, any change, from silence to sound, for example, or from sound back to silence, would be classified as a transient, while the steady, unchanging tone is not a transient.

Transients are impact sounds and get attention more effectively than do steady tones

In audio, for two reasons, the word is used with a somewhat more restricted meaning. The first is connected with everyday listening experience, the second with the performance of audio equipment - microphones, amplifiers, loudspeakers, etc.

The start of any sound, whether sudden or gradual, will reach a listener before the reinforcement of the same sound by reverberation. When the sound finishes, the reverberation goes on. Because this happens all the time around us, our hearing faculty has formed the subconscious habit of paying more critical attention to the beginning of sounds than to the endings.

If the sound builds up relatively slowly, as in the deep notes of a pipe organ, the reverberation builds up almost as rapidly as the direct sound from the pipe. On the other hand, a sound that starts suddenly, like a hand clap, a drum beat, or any sound that has what we may call "impact," reaches the listener well ahead of its reverberation, and gives him a good chance to tell where it came from. Thus musical sounds that have impact, like a hand clap, can be regarded as attention-getting sounds.

Sounds produced by "suddenness" are transients

Any sound distinguished by suddenness is thus a transient; all of the percussion instruments, drums, cymbal, etc., as well as plucked or struck strings; and in speech, the sounds made in pronouncing the letters, b, d, g, k, p, t, are always transients. (Other consonants sometimes are too.)

The second reason for paying attention to this more restricted kind of transient is that audio equipment has particular problems in handling these more "sudden" types of sound, as compared with steady tones of unchanging, or relatively slowly changing, frequency or intensity.