Localization Flashcards

1
Q

How does the auditory system localize?

A

Horizontal plane:

  • ITDs
  • ILDs

Vertical plane

  • Pinna cues
  • Neuroplasticity
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2
Q

What results in ITDs?

A

Physical path differences

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3
Q

What results in ILDs?

A

Head shadow effect

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4
Q

Why are ILDs negligible below 1500 Hz?

A
  • Low frequencies are not attenuated much by the human head, as explained by the head shadow effect
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5
Q

What are the 2 functions of the pinna?

A
  • Collect and amplify sounds

- Localize sounds

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6
Q

How does the pinna collect/localize sound?

A
  • Its unique shape and different cavities produce peaks and notches that help inform a sound’s location in space
  • There are groups of neurons sensitive to these notches
  • The head and pinna form a direction-dependent filter
  • These spectral cues help the auditory system discriminate between front and rear sound sources (Byrne & Noble, 1998)
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7
Q

What higher auditory structures are involved with localization?

A
  • Cochlear nucleus
  • Superior olivary complex
  • Inferior colliculus
  • Auditory cortex
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8
Q

How does the cochlear nucleus localize sound?

A
  • Receives both monaural and binaural inputs
  • Monaural inputs provide spectral notches that contribute to vertical localization
  • Binaural inputs provide ITDs and ILDs
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9
Q

How does the superior olivary complex localize sound?

A
  • It is the most caudal structure to receive binaural inputs
  • The medial superior olivary complex encodes ITDs
  • The lateral superior olivary complex encodes ILDs
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10
Q

How does the inferior colliculus localize sound?

A
  • Sensitive to both ILDs and ITDs
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11
Q

How does the auditory cortex localize sound?

A
  • There are no topographic maps in the cortex

- Multimodal neurons help process a sound’s location in space

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12
Q

How does the squelch effect improve localization with 2 ears?

A
  • Improvement in internal SNR due to interaural comparisons
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13
Q

What is the precedence effect?

A

Describes how the auditory system localizes sound in the presence of reflections

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14
Q

What is localization dominance?

A
  • Occurs when the perception of a sound’s location is dictated by the spatial cues and ITDs of the leading sound perceived by the ears, regardless of the perception of the lagging sound
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15
Q

What is fusion?

A

Fusion results in the perception of a single sound

This occurs when the lead-lag delay is less than the echo threshold.

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16
Q

What are the benefits/limitations of hearing aids in terms of localization?

A

Benefits:

  • Providing audibility
  • Preserving ILDs

Limitations:
- Cannot fix a distorted signal

17
Q

What are the benefits/limitations of cochlear implants in terms of localization?

A

Benefits:
- Preserve ILDs

Limitations:
- Cannot encode ITDs because of electrode array design

18
Q

What are different strategies that can improve localization with hearing aids and cochlear implants?

A
  • Binaural or bimodal fitting
  • Increase bandwidth to provide a wider frequency response
  • Program w/ slow acting compression
  • Implement wireless technology that allows for inter-ear compression
  • Aural rehab. suggests that localization can be relearned