A Narrow-Angle Directional Microphone With Suppressed Rear Sensitivity

Abstract

A novel microphone that enables rear sensitivity to be significantly suppressed has been developed to improve open-air recording quality. Its assembly comprises a line microphone capsule and a second-order pressure gradient directional microphone. In conventional line microphones, residual rear sensitivity causes an influx of unexpected noise, especially at lower frequencies. Our microphone successfully suppresses rear sensitivity by more than 10 dB compared to conventional line microphones in the frequency range below 1 kHz in which major outdoor noise often occurs. Furthermore, it needs no complicated signal processing circuit and can be driven by a normal 48 V phantom power supply. Finally, our microphone was tested in on-the-spot broadcasts. Its rear sensitivity suppression proved to be effective for practical use, and its sound quality was found to be sufficient for use in TV programs. This paper describes the fundamental principle of the microphone's rear sensitivity suppression, the measurement results of its acoustic characteristics and field-test results obtained with it in on-the-spot broadcasts.