frequency-place-transformation

Frequency-Place Transformation AIPA: Models of Auditory Perception Seminar

20 November 2014

The speaker

Francesco Bonadiman [email protected]

Computer Science

Bachelor @UniTN (Trento, IT)

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The outer ear

3/29

The outer ear

3/29

[Raake2014]

The outer ear

3/29

[Raake2014]

catalyzes the sound

The middle ear

[Raake2014]

4/29

The middle ear

[Raake2014]

3 smallest bones in the body

4/29

[Blausen2014] 5/29

2 membrane- covered openings

[Blausen2014] 5/29

2 membrane- covered openings

opposite directions

How it works [Kidsdiscover2014]

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difference of sound pressure


acoustic energy (air) → fluid oscillations

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impedance matching

acoustic energy (air) → fluid oscillations

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The inner ear

[Amplifon2014] 7/29

The cochlea: traditional view

8/29

The cochlea: traditional view

[Zwicker,Fastl2007] 8/29

The cochlea

[Wierstorf2014] 9/29

The cochlea

[Wierstorf2014] 9/29

2½ turns for saving space

The cochlea

[Wierstorf2014]

[RobinsonLibrary2014]

9/29


32 mm “unwound”

The cochlea

[Wierstorf2014]


[Wikipedia2014] 9/29


32 mm “unwound”

The cochlea

[Wierstorf2014]


[Wikipedia2014]

helicotrema 9/29


32 mm “unwound”

Channels and membranes

[Flanagan1972] 10/29



hydromechanically → single unit



fluids = oscillations

Overview [WhatWhenHow2014]

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Overview [WhatWhenHow2014]

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O H R

Is this enough?

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Organ of Corti

[MixBag2014]

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Organ of Corti

[MixBag2014]

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membranes excitation → nervous impulses (firings)

Organ of Corti

[MixBag2014] [Zwicker,Fastl2007]

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Organ of Corti

[MixBag2014] [Zwicker,Fastl2007]

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IHC → brain OHC → tuning


14/29 [GalleryHip2014]

14/29

membranes shearing → HC-cilia → nerve fibers

[GalleryHip2014]

Frequency-Place-Transformation

[Mandel, Ellis2009] 16/29

Frequency-Place-Transformation

[Mandel, Ellis2009] 16/29

BM = kind of Fourier Analysis

Waves and peaks

[Moore2013] 17/29

Waves and peaks

[Moore2013] 17/29

spatial envelope

Waves and peaks

[Moore2013] 17/29

place + growth ← frequency

spatial envelope

Characteristic Frequencies


Characteristic Frequencies


BM’s maximum displacement

Mechanical Reasons [Skidmore.edu2014]

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stiff thick narrow < 0.1 mm


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flexible thinner wider ∼0.5 mm


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[Wikipedia2014]





Von Békésy (1947) Pioneering work Light microscope

Human cadaver ear

Masking

21/29 [Wikipedia2014]

Masking

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shows the limits of frequency selectivity (FPT)

[Wikipedia2014]

Masking

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auditory system → not distinguish between frequencies

[Wikipedia2014]

Masking

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depends on both signal and masker


[Wikipedia2014]

Masking

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Detailed talk about it


depends on both signal and masker


[Wikipedia2014]

Fletcher Experiment


Fletcher Experiment


masker = 65 dB

masked = 40 dB

Fletcher Experiment


masker = 65 dB

masked = 40 dB

NO!

Fletcher Experiment


masker = 65 dB not masked = 55 dB

masked = 40 dB

NO!

Fletcher Experiment



masked = 40 dB

NO! YES!

Fletcher Experiment



masked = 40 dB

NO! YES!

detect the shape of the so-called

Auditory Filters

Auditory Filters (Critical Bandwidth) [AcousticLab.org2014]




USUALLY: sounds located singularly

limited range of frequencies different center frequency



USUALLY: sounds located singularly

limited range of frequencies different center frequency

MASKING: single, broader maximum signal perceived as one same critical bandwidth

BM frequency selectivity = fail

Critical-band Rate Scale

[Zwicker,Fastl2007]

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[Zwicker,Fastl2007]

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new unit leading to critical-band rate scale


[Zwicker,Fastl2007]

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boundaries of the critical bands



[Zwicker,Fastl2007]

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boundaries of the critical bands


audible frequency range in 24 bands


[Zwicker,Fastl2007]

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[Zwicker,Fastl2007]

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from 0 to 24 unit = Bark

(linear)


[Zwicker,Fastl2007]

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higher frequency = bigger amplitude = broader filters from 0 to 24

unit = Bark (linear)


[Zwicker,Fastl2007]

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higher frequency = bigger amplitude = broader filters

mechanical reasons of the membrane

(rigid = high frequencies)

from 0 to 24 unit = Bark

(linear)

Back to the Cochlea

[Zwicker,Fastl2007]

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Back to the Cochlea

[Zwicker,Fastl2007]

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GOLDEN RULE: FPT → Inside our ear, frequencies are mapped onto certain locations

Back to the Cochlea

[Zwicker,Fastl2007]

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SILVER RULE: Mapping not linear but ∼linear up to 500 Hz ∼logarithmic above

GOLDEN RULE: FPT → Inside our ear, frequencies are mapped onto certain locations

References ● Brian C.J. Moore, 2003 - An introduction to the psychology of hearing, 6th Edition

● Zwicker and Fastl, 2007 - Psychoacoustics: facts and models, 3rd edition

● Mandel, Ellis, 2009 - Speech & Audio Processing & Recognition - Lecture 4

● Other slides and scripts from professors Raake and Möller

● Huge help given by www.google.com/imghp to find images and references

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AcousticLab.org: 23 Amplifon: 7 Blausen: 5

Flanagan: 10 GalleryHip: 14 Kidsdiscover: 6

Mandel, Ellis: 16 MixBag: 13 Moore: 17

Raake: 3, 4 RobinsonLibrary: 9 Skidmore.edu: 19

WhatWhenHow: 11 Wikipedia: 9, 19, 21, 22, 23 Wierstorf: 9

Zwicker, Fastl: 8 13 18 24 25 26

www.google.com/imghp



