Abstract

This paper present a sonar system modeled after human spatial hearing and echolocating bats. It’s composed of three transducers, one transmitter which plays the role of the mouth of the bat that transmits echolocating signal and two receivers located respectively near the left ear and the right ear so as to mimic human ears configuration. Inaudible ultrasound echoes captured at the receivers are converted into audible sound using the Doppler shift frequency induced by the user during his movement. The two resulting audible Doppler signals are conveyed binaurally to the user through stereophonic earphones. The amplitude of these audible signals depends on the reflecting properties of the objects detected and their location. It increases as the distance between the system and the object decreases of about 10 decibels per meter. The intensity difference between them increases linearly with the azimuth of 0.34 decibel per degree. Experiments carried out with this sonar system show that it can be helpful to blind people in spatial sensing by supplying information regarding his movement as well as objects movement and their spatial location at the left side, at the right side or in front of him.

Key words: Sonar system, blind mobility aid, spatial hearing, Doppler effect.