Distance Measurement Method Effective from 0 m Using Phase Interference of Audible Sound

Abstract

SUMMARYIn many engineering fields, distance to target is very important information. Typical distance measurement methods use the time delay between transmitted and reflected waves, but it is difficult to estimate short distances. A method for measuring short distances using a standing wave generated by phase interference of transmitted and reflected waves is known in the field of microwave radar. This method is given in a very simple form in which the distance between the microphone and target is estimated as the peak value of the range spectrum, which can be obtained from the Fourier transform of the power spectrum of the observed wave. However, since the minimum measurable distance depends on the bandwidth of the transmitted wave, measurement of shorter distances requires greater bandwidth of the transmitted wave. This paper describes a new distance estimation method that is effective from 0 m based on the phase interference of transmitted and reflected audible sound. Specifically, we introduce an analytic signal instead of the power spectrum and examine the validity and effectiveness of our method by applying it to an actual sound field.