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SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
SIMULATING AND MEASURINGOTOACOUSTIC EMISSIONS
Cecilia Casarini
Master of ScienceAcoustics and Music Technology (MSc)
University of Edinburgh
23rd August, 2016
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
OUTLINE
1 Physiology of the earOuter EarMiddle EarInner Ear
2 Otoacoustic Emissions
3 Cochlear Model
4 Simulations
5 Measurements
6 Conclusions
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Physiology of the ear - OUTER EAR
Pinna (or Auricula):receives sounds from anydirection, responsible ofsound localization.
Ear canal: 2.5 cm long.
Resonant frequencies
f (n) = (2n − 1)cs4l
Eardrum (or tympanicmembrane): vibrates whenpressure wave enters the earcanal
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Physiology of the ear - MIDDLE EAR
Impedance matching between airand fluid to avoid reflection:
Pressure Amplification
Resonant frequencies
Aeardrum
Astapes=
Peardrum
Pstapes= 18.75
Lever action of middle earbones, increasing amplitudeand decreasing velocity,gain= 4.4
Total gain = 4.4 ∗ 18.75 = 82.5
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Physiology of the ear: INNER EAR
Two main functions:
Tonotopy
Active feedback:compressive, non linear
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
OTOACOUSTIC EMISSIONS
Stimulus-based classification:
SOAEs (spontaneous)
SFOAEs (stimuls-frequency)
TEOAEs (transient-evoked)
DPOAEs(distortion-product)
Generation-based classification:
Linear reflection
Nonlinear distortion
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
COCHLEAR MODEL
Three examples of cochlear models:
Neely and Kim (1986): Cochlear Model in the Frequency domain
Elliott (2007): State-space formulation in time domain
Moleti (2009): 1DOF state-space model that also simulatesotoacoustic emissions
Main assumptions:
1 The cochlea is uncurled and modelled as 1D rectangular box(macromechanics)
2 The cochlea is divided in N partitions of independent oscillators(micromechanics)
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
COCHLEAR MODEL
1) 1D transmission line equation for the differential pressure p
∂2pd(x , ω)
∂2x=
2ρ
Hξ(x , t)
Using finite-difference approximation:
FP(t) = Ξ(t),F is invertible =⇒ P(t) = F−1Ξ(t)
2) Micromechanical elements
ξ(x , t) + γbm(x , ξ, ξ)ξ(x , t) + ω2bm(x , ξ, ξ)ξ(x , t) =
pd(x , 0, t)
σbm
State-space formulation:
Z (t) = AEZ (t) + BE (P(t) + S(t))
Ξ(t) = CEZ (t) =⇒ P(t) = F−1Ξ(t) = F−1CE Z (t)
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
COCHLEAR MODEL
Overall state-space equation
MZ (t) = AEZ (t) + BES(t),
where M is the mass matrix of the system:
M = I − BEF−1CE
The mass matrix can be changed in:
Nonlinearity
M = I − BEG (Z )F−1CE ,where:
G (Z ) = B−1C + I
The parameter α determines the nonlinearity of the system:
α(x , ξ, t) = α0
[1− tanh
(1√λπ
∫ L
0
e−(x−x′)2/λ ξ
2(x ′, t)
ξ2satdx ′
)]
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Simulations - TONOTOPY
The basilar membrane has apeak in the cochlear placecorresponding to each inputfrequency
Video Animation of BMmotion
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Simulations - NONLINEAR vs LINEAR
Saturation of the nonlinear active mechanism vs linear case:
α = 0.75 α = 0
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Simulations - TEOAEs
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Simulations - DPOAEs
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Measurements
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Measurements - TEOAEs
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Measurements - DPOAEs
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Measurements - DPOAEs(Model vs Experimental measurements)
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Measurements - DPOEAEs(emissions not detected)
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
Conclusions
Physical Model of the Cochlea:
Strong Linear and Nonlinear Models
Can simulate TEOAEs and DPOAEs
However:
We need a faster model
We should simulate also SOAEs
Work on Latency
Measurements:
Successfully measured DPOAEs
However:
We need a stronger analysis method for TEOAEs and SOAEs
Do more experiments in order to have reliable results and in thefuture substitute audiograms with OAEs screening tests.
SIMULATINGAND
MEASURINGOTOACOUSTICEMISSIONS
Cecilia Casarini
Outline
Physiology of theear
Outer Ear
Middle Ear
Inner Ear
OtoacousticEmissions
Cochlear Model
Simulations
Measurements
Conclusions
THANK YOU!
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