A blind mobility aid modeled after echolocation of bats

Abstract

A new model of a mobility aid for the blind was designed using microprocessor and ultrasonic devices. This mobility aid was evaluated based on psychophysical experiments. In this model, a downswept FM ultrasound signal is emitted from a transmitting array with broad directional characteristics in order to detect obstacles. The ultrasound reflections from the obstacles are picked up by a two-channel receiver. The frequency of the emitted ultrasound is swept from 70 to 40 kHz within 1 ms, so it has almost the same characteristics as the ultrasound a bat produces for echolocation. The frequency of the reflected ultrasound wave is down converted by about 50:1 by using a microcomputer with A/D and D/A converters. These audible waves are then presented binaurally through earphones. In this method obstacles may be perceived as localized sound images corresponding to the direction and the size of the obstacles. From the results of psychophysical experiments, it was found that downswept FM ultrasound was superior for the recognition of small obstacles compared to other ultrasonic schemes. With it a blind person can recognize a 1-mm-diameter wire. It was also proved that the blind could discriminate between several obstacles at the same time without any virtual images. This mobility aid, modeled after the bat's echolocation system, is very effective at detecting small obstacles placed in front of the head.

Experimental evaluation of binaural recording system using a miniature dummy head

“…Other studies examined target detection when blind subjects listened to echoes from a target using a loudspeaker that produced artificial sounds [4,5]. Furthermore, a mobility aid for blind people was developed that used digital signal processing to convert ultrasound echoes from a target into audible sounds in real time [6].…”

Bats Sonar Calls and its Application in Sonar Systems

“…Due to required resources and processor capacity it is likely that multibeam systems will turn to distributed computing on multiprocessor platforms. As mentioned in the work, one of possible applications, which has already been the subject of research of several scientific groups, is to construct a device that would help visually handicapped people to ambulate Abdul et al (2008), Borenstein & Ulrich (1997), Mihajlik et al (2001), Shoval et al (1994), Ifukabe et al (1991). Considering the detail of the problem presented in this chapter and using bat signals and DSP algorithms utilised on an efficient computing platform, construction of such a device seems possible but will require an effort of an interdisciplinary research team.…”

ATAD: Una Ayuda Técnica para la Autonomía en el Desplazamiento

“…Atendiendo específicamente a las ayudas a la movilidad basadas en procesado de imagen y codificación en sonidos, podemos encontrar, entre otras, las siguientes: Sonic Pathfinder (Heyes, 2004), Tyflos (Bourbakis & Kavraki, 2001), Echolocation (Ifukube et al, 1991), vOICe (Meijer, 1992), FIU Project (Aguerrevere et al, 2004), 3-D Space Perceptor (Milios et al, 2003), NAVI (Sainarayanan, 2007), SVETA (Balakrishnan et al, 2006;Aguerrevere et al, 2004), AudioMan (Xu (Kawai & Tomita, 2001), Brigham Project (Lee et al, 2008), The Optophone (Capp & Picton, 2000) o The Cross-Modal ETA (Fontana et al, 2002). La idea general de todas estas ayudas técnicas es la misma: un sistema de captura de imágenes o información del entorno -en algunos casos, es multimodal, como en (Bourbakis & Kavraki, 2001) o basado en ultrasonidos, como el proyecto descrito en (Shoval, 1998) o el Pathfinder-, transmite esa información a un módulo de generación de sonidos.…”