Flush-Mounted Pressure Transducer as a Unit of an Acoustic Homing System

A flush-mounted pressure transducer consisting of a porous plate backed by a cavity is described. The employment of the pressure transducer as an elemental unit of an acoustic homing system is discussed. The homing is executed by the motion of the boundary in a direction and an orientation that brings the pressure transducer system closer to a stationary target. The target is assumed to be a localized acoustic source. The target induces a pressure field on the sensitive surface of the pressure transducer producing the signal in the response. In addition, because of the motion of the boundary, the sensitive surface of the pressure transducer is subjected to the pressure field induced by a turbulent boundary layer. The response of the pressure transducer to this pressure field constitutes the noise. The influence of the motion of the boundary on the nature of the pressure fields to which the pressure transducer is subjected is estimated and the filtering action of the pressure transducer is analyzed in some detail. The design criteria that will tend to maximize the signal-to-noise level of this. type of pressure transducer are derived and discussed. [This work was initiated and sponsored by Systems Application Division, MERDC, Fort Belvoir, Virginia 22060.]