Hearing in Distance

1
Hearing in Distance

• Or Where is that sound?
• Today Isabelle Peretz
• Musical Non-musical Brains
• Nov. 22 _at_ 12 noon Lunch
• Rm 2068B South Building

2
Improving Accuracy

• How do listeners judge distance?
• Metrics of perception
• Absolute distance objective scale
• Euclidean
• Egocentric distance metric in body relations
• Gibsonian (J.J. Gibson)
• Finding a source in distance (Russell, 2004)
• Experiment test distance of a sound source
• 1 - 15 meters
• Blindfolded walk to position or declare distance
  in Euclidean Units
• When are people better?

3
Results of Walk vs. Metric

• Greater accuracy with walking judgments
• Much less variability
• Overestimation of metric close distances
• Underestimation of metric long distances
• Why did we find this result?

4
Is It Just Experience?

• Judge Sound Source
• Walking
• Pull board
• Laying on stomach, walking on hands
• Metrical declaration
• Blindfold listening
• Full vision movement to source position
• Judge distances 2 30 meters

5
Results with the Crawl Experiment

• Walk Crawl very accurate
• Some underestimation at very long distances
• Much more variation with metric judgment
• Tendency for overestimation
• Golfers show improved accuracy judging metric
  distance
• No underestimation tendency at greater distances
  with body-relevant units

6
The Affordance Paradigm

• Why are listeners better judging distances using
  body-relevant actions?
• Use of Affordances
• Gibsons simple idea
• World is perceived in action relevant units
• All perception evolved to support action
• Best perception when subjects interact with
  environment
• Affordances
• Action/body-relevant properties of the world
• Graspable, Eatable, Sitable, Walkable

7
Hearing the Silent World

• Localization
• Study of sound sources
• Sound producing objects relative to listener
• Are sound sources the basis of hearing?
• Visual world
• Light producing objects
• Sun, lamps
• Light reflecting surfaces
• Tables, faces, trees
• Can we detect sound obscuring/reflecting surfaces?

8
Hearing the Silent World

• Sound obstructing surfaces
• Diffuse sound field set behind sound attenuating
  surfaces
• Are listeners sensitive to position of surfaces?
• Test behavioral judgment
• Is the aperture large enough to allow passage?
• Ego-centric judgment facilitates accuracy
• Aperture size affects intensity, spectra
• Randomize intensities, sine wave signals
• Listeners can detect position of sound
  obstructing surfaces

9
Elevation

• Height relative to listener
• How can this be determined?
• Interaural cues?
• Timing difference between the ears
• Mid-Saggital plane
• Loudness difference between the ears
• Absorption by head pinna
• Front-back confusions
• Pinna cues
• Forward, downward facing
• Partially resolve front-back errors

10
Distance

• How far away is a sound source?
• Interaural cues?
• Azimuth does not indicate relative distance
• Pinna cues?
• Slight-downward facing
• More distant cues higher in the perceptual plane

• Salient cues for distance
• Intensity
• Attenuation over distance
• Frequency dependent
• Unreliable indicator
• Reverberation
• Increase in number and lag of echoes
• DEMO