Distance estimation to multiple targets using band‐limited noise signal

In many engineering fields, the distance to target is fundamental and very important information. Acoustical signals, such as audible sound or ultrasound, often play an essential role in measurement of distance. To measure distance, the time delay of the reflected wave measured with reference to the transmitted pulse wave, that is, the time‐of‐flight (TOF), is typically used. However, this method cannot measure short distances because the transmitted wave, which has not attenuated enough at the time of reception of the reflected waves, suppresses the reflected waves for a short distance. Meanwhile, in microwave radar research, a novel method using standing waves has been recently proposed in order to measure the distances to multiple targets, even if short. We apply the fundamental principle of this method to the estimation of short distances for multiple targets using audible sound. In this paper, we focus our attention on audible band‐limited noise. To verify the validity and effectiveness of our method, we perform computer simulations and experiments. It is confirmed that short distances to multiple targets, such as the distances to two targets located 0.1 and 1 m away, can be estimated properly by our method. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(7): 53–60, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ecj.10248