Tomofumi Nakano, Toshihiro Shinohara, Tetsuji Uebo, Noboru Nakasako, Masato Nakayama
PROCEEDINGS OF THE 23RD INTERNATIONAL CONGRESS ON SOUND AND VIBRATION: FROM ANCIENT TO MODERN ACOUSTICS 2016年 査読有り
In order to achieve the realistic sensation of sound, sound field reproduction technique plays a very important role. The sound field reproduction technology is roughly classified into binaural and transaural reproduction systems. The former has a merit that it can be implemented in small scale systems under the assumption of the headphone listening but it is somewhat burdensome to wear the headphone. Although the latter does not require headphones, it requires large scale system to reproduce the sound field. In this paper, we focus on the development of small scale sound reproduction system. If the distance between sound source and listener is a priori known, it may be possible to reproduce the sound field more accurately. As a method of distance estimation for a target, acoustical distance measurement (ADM) was proposed based on phase interference using audible sound. However, measurement of audible sound has the potential to record private information such as conversation, which may yield a privacy issue. There is a reproduction method of sound field by parametric loudspeaker using ultrasonic sound. Therefore, in order to reproduce sound field more accurately, protecting personal conversation from the sound measurement, this paper describes a new method to estimate the distance using an ultrasonic wave. This acoustic distance measurement is based on interference between direct wave and reflected wave using ultrasonic wave. First, the composite wave of direct wave and reflected wave is observed, and then the power spectrum of the composite wave is obtained by Fourier transform. The power spectrum of composite wave is a periodical function whose period is inversely proportional to the distance between microphone and target. Finally, by applying Fourier transform again to the power spectrum, the range spectrum is obtained, whose peak position corresponds to the distance. To confirm the effectiveness of the proposed method, it is applied to the actual situation of distance measurement by using ultrasonic sound.