The appearance of cavitation and the characteristics of cavitation acoustic pulse are investigated about decelerated flow as well as accelerated flow in blowdown-type cavitation tank without recirculating water. The pressure pulses are monitored by measuring the peak pulse amplitude in a long orifice, where separation bubbles are formed but the remarkable hysteresis effect is found. The appearance of cavitation is well correlated with the count-rate of pressure pulses and the acoustic energy level. The count-rate of pressure pulses is related qualitatively with the total acoustic energy of pressure pulses and it varies exponentially with the threshold level. The extent of cavitation in growth is devided in several stages from the appearance of cavitation and the characterics of pressure pulses.
