Abstract: Experimental studies on noise characteristics of a IS65-50-160A centrifugal pump were carried out using near-field acoustic pressure method on an open test bench, during which the variation and frequency characteristics of pump noise versus net positive suction head were investigated at variable and constant flow rates, while an analysis performed to the influence of flow rate, net positive suction head and air volume at pump suction inlet on the A-weighted sound pressure level and the sound pressure level at different frequencies. Results show that the A-weighted sound pressure level increases with the flow rate and reaches the maximum in the high efficiency range under non-cavitation conditions. A-weighted sound pressure level decreases significantly in the beginning of cavitation occurrence, but rises greatly when cavitation is fully developed. The sound pressure level respectively with high frequency of 1 000 Hz and 2 000 Hz has significant contribution to the overall A-weighted sound pressure level. The sound pressure level at most flow rates has peak values at 250 Hz and 1 000 Hz, which is related with the blade passing frequency. During the cavitation process, which is induced by regulating the inlet pump valves to keep the flow rate constant, the A-weighted sound pressure level drops obviously due to air entrained from the pump inlet; the characteristic frequency of pump for cavitation test is 250 Hz, in which case the difference of peak pressure level between cavitation and non-cavitation situation is within 5.9-16.4 dB.