Transient sounds

Transient sounds are aperiodic sounds which come and go quickly. Examples from everyday life are a knock on a door, the sound of one piece of cutlery rattling against another, or a firework exploding. In speech, the main source of transient sounds is the explosive release of a closure, such as releasing a closure for [p] or [k]. Other common transient sounds in speech are the tongue or lips coming apart as someone starts to speak, bubbles of saliva bursting in the mouth, the velum being raised, or the sides of the tongue making contact with the teeth or cheeks.

In a waveform, transients show up as a spike. On spectrograms, they appear as dark vertical lines which last only a short time.

In Figure 3.3, there are two transients. One, at about 0.25 s, corresponds to the lips opening for the sound [p], the other, marked with the box just after 0.6 s, corresponds to the tongue coming away from the alveolar ridge, for [d].

Figure 3.6 shows the waveform of a transient (the start of [d] in ‘spend’) in more detail. The transient portion T lasts less than 30 ms. It has an abrupt start and then fades away.