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

Abstract

In many engineering fields, distance to target is very important information. Typical distance measurement methods use time delay between transmitted and reflected waves, but it is difficult to estimate short distance. On the other hand, a method for measuring short distances using a standing wave, which is 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 such that the distance between microphone and target is estimated as a peak value of the range spectrum, which can be obtained by Fourier transform of the power spectrum of the observed wave. However, since the minimum measurable distance depends on the bandwidth of the transmitted wave, the shorter distance measurement requires the wider bandwidth of the transmitted wave. This paper describes a new distance estimation method measurable from 0m based on the phase interference of transmitted and reflected audible sound. More concretely, 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.