Question

what is pulse in sound

Answer 1

music and music theory, the pulseconsists of beats in a (repeating) of identical yet distinct periodic short-duration stimuli perceived as points in time occurring at the mensural level

Answer 2

the pulse may be audible or implied.
if a pulse become too fast it would become a drone, one which is too slow is perceived as inaudible sound.
Musical pulse are generally specified in range
40-240 beats per minute.
this is often most designated as crotchet or quarter note