距離の測定は基本的かつ重要な要素技術であり，レーザrn光や電波（マイクロ波，ミリ波等），音響信号が利用されてrnいる。音響信号を用いた測距の場合，測定対象物に向けてrnパルス音を送出し，それが反射波として返ってくるまでのrn時間を計測して距離を求める方法が一般的である。複数rnの測定対象物がある場合は，各村象物に対応した複数の反rn射波が観測されるので，それぞれの時間遅れを計測すれば，rn各対象の距離が求められる。しかしこの手法は，送信パルrnスが十分減衰しないうちに反射波が返ってくるような近いrn距離に測定対象物がある場合には，反射波が送信波に埋もrnれてしまい，測定不可能となる。%In many engineering fields, distance to target is fundamental and very important information. Acoustical signal, such as audible sound or ultrasonic, often plays an essential role in measurement of distance. To measure distance, the time delay of reflected wave measured with reference to transmitted pulse wave, i.e. time-of-fiight (TOF) is used typically. This method, however, can not measure short distance because the transmitted wave, which has not attenuated enough as of reception of reflected waves, suppresses the reflected waves for short distance. Meanwhile, in the research field of microwave radar, to measure distances to multiple targets even if short, a novel method by using standing wave has been recently proposed. We apply the fundamental principle of this method to estimation of short distance 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. As a result, it has been confirmed that short distances to multiple targets, such as the distances to two targets located at 0.1m and lm, can be estimated properly by our method.
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