Slide 1

Transcript Slide 1

Lyon’s Cochlear Model
Meena Ramani
01/24/2005
Cochlea
Apex
4mm2
1mm2
Base
32-35 mm long
High Freqs
Low Freqs
Lyon’s Cochlear Model
Lyon’s Cochlear Filters Banks
Frequency response of the filter bank for fs=16Khz
20
– 5 coefficients
• Command:
– DesignLyonFilters
• Required parameter:
– Sampling frequency fs
• Depending on fs the no of
filter banks vary
10
0
Amplitude response
• A single stage:
– Notch filter
– Resonant filter
• Second order filters
-10
-20
-30
-40
-50
-60
2
10
3
10
Logarithmic (base 10) frequency
4
10
HWR and AGC
•
LyonPassiveEar(x,fs)
– Calculates the probability of firing along the auditory nerve due to an input sound x
(required) and a sample rate fs (required)
Models the HWR which is produced by the IHC
agc(input,coeffs)
– The feedback mechanism of the OHC is modeled by AGC
– AGC changes gain by steps to be below a target value
AGC charactersitics for input stream of 20 ones: step size 0.5 for different target values
1
0.4 Target value
0.9
0.5 Target value
0.8 Target value
0.8
0.7
Amplitude
•
•
0.6
0.5
0.4
0.3
0.2
0.1
0
0
2
4
6
8
10
Time
12
14
16
18
20
Center Frequencies for Lyons's cochlear model fs=44100 No of channels 118
120
X: 0.08382
Y: 118
Apex
Channel number
100
vs.
Center Frequencies
Channel Number
80
X: 3.049
Y: 62
60
40
20
Base
X= 21.0366
Y= 1
0
22
20
18
16
14
12
10
8
Center Frequency (KHz)
83Hz-3Khz (~3Khz range)56 filters
3Khz-21Khz(~ 18Khz range)61filters
6
4
2
0
More importance to
Low frequencies
Cochleogram showing Place coding for sine wave f=1Khz; fs=44.1Khz
10
30
Cochleogram
for 1Khz sine
40
50
60
70
80
90
100
110
20
40
60
80
100
Samples decimated in time by 20
120
Center Frequencies for Lyons's cochlear model fs=44100 No of channels 118
100
X: 1.066
Y: 91
80
Channel Number
Lyon's Cochlea Model Bands
20
60
40
20
0
3.5
3
2.5
2
1.5
1
Center Frequency (KHz)
0.5
0
Cochleogram showing Place coding for sine wave of f=1Khz and f=3Khz; fs=44.1Khz
10
30
Cochleogram
for 1Khz+3Khz
sine wave
40
50
60
70
80
90
100
110
20
40
60
80
100
Samples decimated in time by 20
Center Frequencies for Lyons's cochlear model fs=44100 No of channels 118
120
100
X= 1.0663
Y= 91
80
Channel Number
Lyon's Cochlea Model Bands
20
X= 3.0487
Y= 62
60
40
20
0
5
4
3
2
1
Center Frequency (KHz)
0
Cochleogram showing Place coding for sine wave f=1Khz with added pink noise
1Khz With added noise
Cochleogram showing Place coding for sine wave f=1Khz;
20
Lyon's Cochlea Model Bands
Pink
noise
10
30
40
50
60
70
10
80
10
20
30
30
40
50
60
70
Samples decimated in time by 20
80
90
100
40
Cochleogram showing Place coding for sine wave with added white noise f=1Khz;
50
60
10
70
20
80
10
20
30
40
50
60
70
Samples decimated in time by 20
80
90
100
White
noise
Lyon's Cochlea Model Bands
Lyon's Cochlea Model Bands
20
30
40
50
60
70
80
10
20
30
40
50
60
70
Samples decimated in time by 20
80
90
100
Vowel /i/
F1 Hz F2 Hz F3 Hz
270
2290 3010
Cochleogram showing Place coding for sine wave of /i/vowel
10
30
40
50
Center Frequencies for Lyons's cochlear model
100
60
X= 0.2703
Y= 90
90
70
80
80
90
70
200
400
600 800 1000 1200 1400 1600 1800 2000 2200
Samples decimated in time by 20
Channel Number
Lyon's Cochlea Model Bands
20
60
X= 2.2456
Y= 49
50
X: 3.036
Y: 40
40
30
20
10
0
12
10
8
6
4
Center Frequency (KHz)
2
0
-4
Center Frequencies for Lyons's cochlear model
x 10
90
10
3.5
80
20
3
70
2.5
60
30
Channel Number
Lyon's Cochlea Model Bands
Cochleogram showing Place coding for 'tapestry.wav'
40
2
50
1.5
60
50
40
30
1
70
20
0.5
80
10
50
100
150 200 250 300 350 400
Samples decimated in time by 100
450
500
0
8
7
6
5
4
3
Center Frequency (KHz)
2
1
0
Spectrogram of 'tapestry.wav'
1
0.9
0
0.8
Frequency
0.7
-20
0.6
-40
0.5
0.4
-60
0.3
-80
0.2
0.1
-100
0
0
0.5
1
1.5
Time
2
2.5
4
x 10
For Speech Sentence
Thanks