Acoustics / Electroacoustics
A sound with a short ENVELOPE, usually with a less sharp ATTACK than a CLICK. Also called an impulse.
Compare: GRAIN, IMPACT SOUND, TRANSIENT.
With frequencies below about 20 Hz, individual oscillations may be heard or sensed as slow pulses of pressure variation without PITCH characteristics.
See: AMPLITUDE MODULATION, BEATS, INFRASONIC, RUSTLE NOISE, SONAR.
Sound Example: Pulsating ventilation duct, Burrard Dry Docks, Vancouver, B.C.
In electronics, the pulse is a rectangular DIRECT CURRENT voltage SIGNAL produced by a pulse GENERATOR. Its form could be described as an on-off voltage, where the 'on' voltage has a duration of t1 and is repeated after an interval of t2, during which the voltage drops to the 'off' level. Pulses can be used to control a SWITCH. Compare: RECTIFICATION.
A pulse wave is an ALTERNATING CURRENT signal, whose WAVEFORM contains both positive and negative sections. The ratio of the 'on' to 'off' times of the waveform is called the duty cycle. The pulse wave may be distinguished from the SQUARE WAVE in that the latter has a duty cycle of 1:1. Compare: SAWTOOTH WAVE, TRIANGLE WAVE.
Sound Example: Pulse wave with a 1:4 duty cycle.