L13. Sound Localization - Cornell University · C lli l 13 Colliculus • Lateral lemniscus •...
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9/16/2011 1 1 L13. Sound Localization September 16, 2011 BioNB4240 C. D. Hopkins Krogh’s Principle Linear Summation Delay‐line Coincidence Detector Σ + Σ delay Σ ‐ ∫ ∞ ∞ − ⋅ + = dt h t f r ) ( ) ( ) ( τ τ τ The mobbing calls of different species of birds, given in response to a sitting predator (cat, owl). 3 Sound spectrograms of mobbing calls from 5 species of British birds (Marler, 1955) Marler, P. (1955). The characteristics of certain animal calls. Nature 176, 6‐7. Aerial alarm calls of different species of birds are very similar. Alarm calls of 5 species of British birds given in response to spotting an overhead hawk. 4 (Marler, 1955) Chickadee sees predator sitting in tree. Mobbing calls attract flock members to alert other birds. sharp onset click‐like broad bandwidth 5 repetitive •slow onset and offset •whistle‐like •narrow frequency range •not repeated Robin sees a hawk Alarm Call (warns baby birds) 6
Transcript of L13. Sound Localization - Cornell University · C lli l 13 Colliculus • Lateral lemniscus •...
9/16/2011
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L13. Sound Localization
September 16, 2011
BioNB4240C. D. Hopkins
Krogh’s Principle Linear Summation Delay‐line Coincidence Detector
Σ+
Σ
delay
Σ‐
∫∞
∞−
⋅+= dthtfr )()()( τττ
The mobbing calls of different species of birds, given in response to a sitting predator (cat, owl).
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Sound spectrograms of mobbing calls from 5 species of British birds (Marler, 1955) Marler, P. (1955). The characteristics of certain animal calls. Nature 176, 6‐7.
Aerial alarm calls of different species of birds are very similar.
Alarm calls of 5 species of British birds given in response to spotting an overhead hawk.
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(Marler, 1955)
Chickadee sees predator sitting in tree.
Mobbing calls attract flock members to alert other birds.
sharp onset
click‐like
broad bandwidth
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repetitive
•slow onset and offset•whistle‐like•narrow frequency range•not repeated
Robin sees a hawk
Alarm Call (warns baby birds)
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Why are the mobbing calls so similar?
Marler’s Hypothesis:
“chatter” calls are easily locatable (ideal for calling attention to where the owl is hiding)
1) Sh d ff i l i ioscillogram of
d
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1) Sharp onset and offset inter‐aural timing cues.
2) Repetitive redundant.
3) Broad bandwidth‐ low frequencies provide good phase cue‐ high frequencies provide good inter‐aural
amplitude cue (shadow of head)
sounds
Why are the hawk calls similar?
Marler’s Hypothesis:“Tseet” sounds are difficult to locate (ideal for
alerting conspecifics and young to look up and hide).
1. gradual sound onset and offset – poor timing
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1. gradual sound onset and offset poor timing cue
2. too high freq for phase determination. 3. too low frequency for sound shadowing.
sound localization
Humans have difficulty locating 3 kHz tones.
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Steven and Newman, 1934phase ambiguity when λ < d
dd
fc=λ
Binaural CuesTwo cues for Cats:
ITD
IID = ILD
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ITD: (varies between 0 and 400 microsec)
ILD is strongest at high frequencies >5 kHz for cats, >2 for humans
d = .136 mITD = 0.136 m / 340 m/s
Auditory pathways
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dorsal view
mammalian brain
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Auditory Pathway Wiring• Cortex
• Thalamus
• Inferior C lli l
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Colliculus
• Lateral lemniscus
• Brainstem
lateral superior olive
LSO receives inputs from 2 sides
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medial nuc. trapezoid body
LSO responds to ILD
contralateral intensity
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Auditory Pathway Wiring• Cortex
• Thalamus
• Inferior C lli l
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Colliculus
• Lateral lemniscus
• Brainstem
medial superior olive
Cells in MSO act as coincidence detectors
• MSO neurons fire best when stimulated with a particular ITD. Using sine waves, this means one particular phase
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difference.• MSO units phase lock to
monaural and to binaural stimulation.
• Best IPD corresponds to difference in response phases for two ears. MSO is a coincidence detector.
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Cells in MSO act as coincidence detectors
• MSO neurons fire best when stimulated with a particular ITD. Using sine waves, this means one particular phase
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difference.• MSO units phase lock to
monaural and to binaural stimulation.
• Best IPD corresponds to difference in response phases for two ears. MSO is a coincidence detector.
Jeffres’ Model (1948)
• Suppose Right & Left neural inputs from opposite sides converge....
• Delays, from neuronal conduction
• Output cells (A E) fire only if
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• Output cells (A‐E) fire only if there is coincident inputs from both R and L
• Delay‐Line + coincidence detector produces a map of azimuth.
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Barn OwlBarn Owls
• R. Payne (1971)* establishes that barn owls use passive listening to detect and localize prey.
Roger Payne
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• owls turn head toward sound.
• leave perch, track sounds.
• owl attacks sound, not mouse.
• Owls are using passive listening (not echolocation!)
* Payne, R. S. (1971) Acoustic location of prey by Barn owls (Tyto alba)
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Owl can “localize” before leaving perch.
Owl attack is precise within 2 degrees.
Owl attacks sound source, not the mouse.
•Conclusion: good localization in both vertical
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vertical(elevation) and horizontal (azimuth)
•How do they localize in the vertical?
Ear Asymmetry in Barn Owls
Asymmetry in ear openings direct sound from above or below.
A d i i i i i l l
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As sound position varies in vertical angle: ILD in two ears.
In barn owls, asymmetric ear placement converts IID into map of elevation
0 4
0.6
0.8
1 y= x2
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Right earLeft ear
0 0.5 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
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In barn owls, asymmetric ear placement converts IID into map of elevation
0 4
0.6
0.8
1 y= x2
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Right earLeft ear
0 0.5 1-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
to be continued…..
