Directivity based control of acoustic radiation

Abstract

A novel concept of local noise control along specific receiver directions is demonstrated by controlling the directivity of the radiated noise. This method is particularly useful for practical low frequency noise where global noise control is difficult to attain. The directivity pattern of the radiator is controlled by attaching a lumped mass. Arbitrary placement of the point mass on the radiator is shown to increase the acoustic radiation. The mass location to minimize sound pressure in a target direction is obtained using an optimization technique. The possibility of local noise control for target receiver locations in different directions to the radiator is demonstrated and the underlying physical mechanisms are discussed in detail. The reduction of sound pressure at the receiver location with a lumped mass at the optimal location is shown to be much more than that achievable by a uniform distribution of the point mass over the plate. Furthermore, design guidelines are extracted from the computed results which can be of aid to the field engineer.