Perception 5

• What is one of the learning objectives related to sound localization?

  Describe the cues used to determine the location of a sound source

  
• How does location information in vision compare to audition?

  Visual information for the relative location of objects is contained within the retinal image
• What does the place activated by a sound on the cochlea indicate?

  It does not indicate the location of the sound
• What are the two types of cues used to localize sound?

  Binaural and monaural cues

  
• What do binaural cues require for sound localization?

  Comparison of signals in the left and right ears

  
• What are interaural time differences (ITDs)?


  The differences in the time it takes for a sound to reach each ear

  
• What are interaural level differences (ILDs)?

  The differences in sound pressure level reaching each ear

  
• What do monaural cues help localize?

  The elevation and distance of a sound

  
• What is one of the monaural cues related to sound localization?

  Filter properties of the pinna (outer ear)
• What are the three dimensions of sound location?

  Azimuth, elevation, and distance
• How does the arrival time of sound at the ears depend on its location in azimuth?

  The relative time a sound arrives at the two ears depends on its location
• What happens when a sound source is straight ahead?

  The distance to each ear is the same, and there’s no difference in time
• What occurs when a sound source is positioned to one side?

  The sound will reach the nearer ear first
• What is the typical speed of sound through air?

  Approximately 330 m/s
• What is the maximum interaural time difference (ITD) in humans?

  Approximately 600 μs (0.6 ms)
• For which type of sounds is ITD most useful?

  Low frequency/abrupt-onset sounds
• How does the relative sound pressure level reaching the two ears depend on the source location?

  It depends on the location of the source in the azimuth
• What causes a reduction in sound level for the far ear?

  The acoustic shadow created by the head

  
• For which type of sounds does the reduction in sound level occur?

  High-frequency sounds (e.g., 7 kHz)
• Where does the processing of ITDs and ILDs begin?

  Within the brainstem in the superior olivary complex
• What type of neurons are located in the lateral superior olive?

  Neurons sensitive to interaural level differences (ILDs)
• What type of neurons are located in the medial superior olive?

  Neurons sensitive to interaural time differences (ITDs)
• What complementary information do ITDs and ILDs provide?

  Information about azimuth (left-right) location
• For which type of sounds do ITDs work especially well?

  Low-frequency sounds
• What do binaural cues not provide information about?

  Elevation and distance
• What is the cone of confusion?

  A set of points from which a sound source will produce identical ITDs and ILDs
• What do monaural localization cues help determine?

  Elevation and distance of a sound

  
• How do filter properties of the pinnae affect sound localization?

  They change the relative intensity of different frequencies based on sound source elevation
• How does artificially altering ear shape affect sound localization?

  It impairs or damages the ability to localize sound elevation
• How does sound intensity relate to distance?

  Sound intensity decreases with distance
• What does reverberation indicate about sound distance?

  It provides a cue to distance based on how sound reflects off objects
• How does the distance of a sound source affect direct and reverberant sounds?

  It changes the relative intensity and timing of direct and reverberant sounds
• What challenge do reflected sounds pose for localization?

  They make it difficult to determine the true number and location of sound sources
• What is the precedence effect?

  Similar sounds arriving in quick succession are localized according to the direction of the first sound
• What is the time frame for the delay in the precedence effect?

  Less than 10-20 ms
• What is one of the learning objectives related to auditory grouping?

  Understand the basic principles of auditory grouping
• What does auditory scene analysis involve?

  Making sense of the mixture of component sounds in natural environments
• What does the auditory system need to do with the components of sound?

  Segregate components from different sound sources and group components from the same source
• What principles does auditory grouping follow?

  Many analogous principles similar to visual grouping
• What is one principle of auditory grouping?

  Common fate