Localization Flashcards
How does the auditory system localize?
Horizontal plane:
- ITDs
- ILDs
Vertical plane
- Pinna cues
- Neuroplasticity
What results in ITDs?
Physical path differences
What results in ILDs?
Head shadow effect
Why are ILDs negligible below 1500 Hz?
- Low frequencies are not attenuated much by the human head, as explained by the head shadow effect
What are the 2 functions of the pinna?
- Collect and amplify sounds
- Localize sounds
How does the pinna collect/localize sound?
- 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)
What higher auditory structures are involved with localization?
- Cochlear nucleus
- Superior olivary complex
- Inferior colliculus
- Auditory cortex
How does the cochlear nucleus localize sound?
- Receives both monaural and binaural inputs
- Monaural inputs provide spectral notches that contribute to vertical localization
- Binaural inputs provide ITDs and ILDs
How does the superior olivary complex localize sound?
- It is the most caudal structure to receive binaural inputs
- The medial superior olivary complex encodes ITDs
- The lateral superior olivary complex encodes ILDs
How does the inferior colliculus localize sound?
- Sensitive to both ILDs and ITDs
How does the auditory cortex localize sound?
- There are no topographic maps in the cortex
- Multimodal neurons help process a sound’s location in space
How does the squelch effect improve localization with 2 ears?
- Improvement in internal SNR due to interaural comparisons
What is the precedence effect?
Describes how the auditory system localizes sound in the presence of reflections
What is localization dominance?
- 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
What is fusion?
Fusion results in the perception of a single sound
This occurs when the lead-lag delay is less than the echo threshold.