harmonicity winner-take-all the cochlea is a sensitive membrane structure in the inner ear that...
TRANSCRIPT
Harmonicity Winner-Take-All
The cochlea is a sensitive membrane structure in the inner ear that performs a particular type of frequency analysis.
While most applications treat the cochlea like an FFT, this is a poor description.
The point is that for a given input frequency, many points on the cochlea respond, butWith different amplitudes and different phases.
1) While it is true that the cochlea extracts frequency, the tuning is broad.
2) Unlike the FFT and spectrogram representations, frequency tuning is foundlogarithmically represented along the length of the cochlea andin the hair cell population.
3) At the frequencies for much of speech, the hair cells in the cochlea canreport the relative phases of the waveform for a particular frequency
Spectrogram
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Linear vs. Log Frequency Coding
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Harmonic sounds
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Because many phases of a tone are found in the cochlear representation, aharmonic sound will excite a subset of cochlear hair cells to fire in synchronyat a period equal to the fundamental frequency.
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cos(x), cos(2x), cos(3x)
Inhibitoryneuron
Hair cells from the cochlea - different best frequencies
Inhibitoryneuron
Hair cells from the cochlea - different best frequencies
By making the inhibitory neuron leaky, temporally-jittered inputs leak away before theircontributions add up.
When synchronized inputs come in, those neurons fire together, driving the inhibitoryneuron at the same time. This barrage of inputs make the inhibitory cell fire immediately.
The inhibitory cell then shuts everyone down. Only the synchronized pattern getsthrough.
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Two harmonic sounds summed
Can we pull these apart?
Chip Idea:
1. Given a cochlea circuit in PSPICE, design the hair cells and inhibitory networkneurons and demonstrate the synchrony concept.
2. Show that harmonic sounds are preferentially passed through and that thenetwork can briefly lock onto one harmonic sound over another.