Killer whales, blind bats, discriminating dolphins, ma...(8) A SONAR SYSTEM FOR THE BLIND Echol...)
8) A SONAR SYSTEM FOR THE BLIND
Echolocation is a method of perceiving the world by emitting noises, then listening to the reflections of these noises off objects in the environment. Animals use echolocation for hunting and navigation, but visually impaired humans also employ echolocation as part of their orienting repertoire while navigating the world. There are a few rare individuals who can echolocate very well without assistance. However, researchers at Boston University have developed a prototype device that can enhance auditory cues while navigating an environment. The device repeatedly emits an inaudible (to humans) ultrasonic click several times per second, and each click reflects off any objects in the environment. The reflections are then detected by special head-mounted microphones, and computer processing converts the ultrasonic signals into audible signals, which the user then can hear over custom open-ear earphones.
The end result is an "auditory image" in which objects in the environment seem to emit "sounds" to the user, with objects of different shapes and textures emitting subtly different sounds, such that the user can distinguish between them. According to BU researcher Cameron Morland (cjmorlan@bu.edu), the unique acoustic characteristics of the reflections enable the user to better distinguish the location and size "surface" properties of objects. For instance, sounds emitted by an object to the left will arrive at the left ear a bit sooner and louder (interaural time difference and interaural level difference).
Furthermore, sweeping the device over a surface while remaining the same distance from it, will produce a reflection with unchanged velocity of the surface of an object is flat. If the surface is tilted so it moves closer to the user, it will sound higher in pitch; tilted the other way, it will sound lower in pitch (a Doppler shift). A roughly textured surface will have so
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| Contact: Jason Bardi jbardi@aip.org 301-209-3091 American Institute of Physics Source:Eurekalert |
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