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Hearing the Silent World

Explore the fascinating world of echolocation and test your ability to detect properties of objects using sound waves. Engage in interactive tasks with an assistant, differentiate between hard and soft objects, big and small items, and objects of similar size but different shapes. Can you echolocate objects accurately? Delve into the impact of object properties on sound, concluding with acoustic occlusion results. This interactive experiment also investigates the limits and potential of human echolocation, drawing insights from research and real-life examples like Dan Kish. Unlock the mysteries of echolocation and the extraordinary abilities of the human senses.

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Hearing the Silent World

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  1. Hearing the Silent World The Bounce of Sound

  2. TLA: Echolocate in Space • Purpose: • Can you echolocate? What properties of objects can you detect? • Ingredients • Assistant? • Hard & Soft object • Big and small object • Similar size, differently shaped objects • Pick two or three tasks • Try to echolocate objects and determine properties • Allow 30 seconds acoustic exploration • Make a guess • Assistant marks right/wrong picks next object • Can you echolocate at better than chance? • How did the properties of objects make them sound different

  3. Finishing up with Acoustic Occlusion • Previous results • Short Ss judge more apertures as ‘passable’ than tall Ss • Louder intensities • Increases likelihood of judged passability • Scaling factor • Sine-wave • No spectral information • No effect on judgments • d’ sensitivity • Highest in louder intensities • How did they do it? • Detect change across aperture expanse • Not the cue to intensity • Change in intensity over space

  4. Facial Vision • Why don’t blind people bump into things? • Diderot (mid 18th century); Hayes (1935) • Facial vision • Pressure to allow surface detection • Supa, Cotzin & Dallenbach (1944) • Sound or Pressure • Both may contribute • Survey of blind individuals (1940’s) • 1/3 Facial vision; 1/3 Sound; 1/3 uncertain

  5. Testing FV vs. Echolocation • Walk to wall in front of you • Stop at closest point of detection • Stop as close as possible • Vary skin covering • Plastic wrap on exposed skin • No effect; subjective reports of ambiguity • Face/no face coverage • Some effect; performance degredation • Sound conditions • Vocal noise • No effect; subjective reports of distraction • Shoes • Some effect; performance degradation • Shoes + Facial cover • Highest echolocation difficulty • What Happened??? • Ear muffs problem

  6. How good is human echolocation? • Dan Kish • Congenitally blind human echolocator • First certified (blind) blindness mobility instructor • Team BATS • Blind mountain biking team (Dan Kish) • Sighted leader + Dan • Hears and navigates around novel areas • Counts landmarks to find route

  7. Limits of Human Echolocation • Texture detection • Clothe, wood, glass, metal • Blind differentiate wood and cloth, metal/glass confusion • Hard vs. Soft • Shape detection • Differentiate circle from square from rectangle etc. • Equal area, differing reflectance properties • Object detection • Close object advantage • Disc detection as small as 5 cm** and string • Use of head-movements

  8. Information for Human Echolocation • Close distances (within 2 m) • Ripple noise pitch: interference between emitted and reflected sound • Total intensity: greatest with close sound board • Far distances (greater than 2 m) • Time delay of reflected sound • Intensity ratio: emitted to reflected • For moving listeners • Doppler shift: used by bats, high speed • Auditory Time-to-contact: dilating reflective surface

  9. Echolocation Research • Can sighted listeners echolocate? • Early experiments - yes with some training • Ask listeners to stop before contact with a wall • After 20 trials avoid contact • Can detect the distance of a wall in front of them up to 7 meters away • Better while moving

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