Abstract
This paper describes a directive spectrum analyzing system using two microphones, one of which is fixed and the other revolves around the fixed one. In this system, the direction of the main lobe of the directivity can be arbitrarily changed on the plane of revolution by adjusting the delay time given to the outputs of the microphones. The sound to be analyzed should be stationary during the period of revolution. A unibeam directivity is achieved when the outputs of the microphones are delayed so that the delayed signals are in phase for the incident sound from a specified direction. After providing the adequate delay time, the power spectra and cross spectrum are computed during a full turn of the revolving microphone, and the power spectrum of the incident sound from the specified direction is estimated.
