In music theory, the pulse is a series of uniformly spaced beats—either audible or implied—that sets the tempo and is the scaffolding for the rhythm.
So while the rhythm may become too difficult for an untrained listener to fully match, nearly any listener instinctively matches the pulse by simply tapping uniformly, despite rhythmic variations in timing of sounds alongside the pulse.
The pulse is not necessarily the fastest or the slowest component of the rhythm but the one that is perceived as basic.
Like the tick of a metronome or a watch, pulses mark off equal units in the temporal continuum.... A sense of regular pulses, once established, tends to be continued in the mind and musculature of the listener, even though the sound has stopped....
In fact there is a natural tendency to perceptually group or differentiate an ideal pulse in this way.