A STUDY OF A NEGATIVE IMPULSIVE WAVE GENERATOR

A compression wave discharged from the open end of a tube causes posit ive impulsive noise. Active noise cancellation, which is the cancellin g of the noise by the addition of an inverse wave, is a useful techniq ue for reducing impulsive noise. The main objective of this study is t o present the design for a negative impulsive wave generator utilizing unsteady mass influx. In this paper, in order to clarify the relation ship between the unsteady mass influx and the negative impulsive wave, numerical and aeroacoustic analyses have been carried out using an un steady expansion wave discharged from the open end of a shock tube, to gether with the experimental investigations. As a result, the effect o f an unsteady expansion wave on a negative impulsive wave is shown. (C ) 1996 Academic Press Limited