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1
Analysis and Synthesisof Pathological Vowels
Prospectus
Brian C. Gabelman
6/13/2003
2
OVERVIEW OF PRESENTATION
I. Background
II. Analysis of pathological voices
III. Synthesis of pathological voices
IV. Summary
3
What is this project?
BACKGROUND
Methods for modeling, analysis, and synthesis of pathological vowels incorporating novel approaches in:
- System identification- Parameterization of non-periodic
components (AM, FM, and noise)- Synthesizer designs for realtime and
offline use
What is a pathological vowel?
May be caused by physical or neural problems. Characterized by substantial and complex NONPERIODIC signal components.
4
Why do it?- Create a non-subjective basis to
compare pathological voices for:1. Improved diagnosis2. Tracking changes in a patient’s voice
- Generate voice samples with known levels of variations (noise, roughness, etc.)for:1. Evaluation of model parameters2. Evaluation of listener variability3. Evaluation of importance of levels
of pathological features.
BACKGROUND
What has been done before?- A well-established theory existsfor NORMAL voices
- Recent studies of pathological voicesemploy perturbation of normal features plus additive noise.
- ES (external source) stimulation of the vocal tract to analyze formants (vowels)since 1942 for NORMAL voices.
5
For the theoretical/analytical aspect of the project, an expression of the hypothesis of the dissertation in one sentence is:“By means of FM and AM demodulation techniques, estimation of nonperiodicfeatures of pathological vowels may be improved.”
BACKGROUND
6
GLOTTAL SOURCE WAVEFORM
(time domain)
VOCAL TRACT FREQ. RESP.
(freq domain)
RESULTING
VOICE SIG.
(time domain)
g(t)G(s)
f(t)F(s)
v(t)V(s)
g(t) conv. f(t) = v(t) (time domain)G(s) x F(s) = V(s) (freq domain)
ANALYSIS
SOURCE - FILTER MODEL OF SPEECH
7
Steps for analysis:
PERIODIC ANALYSIS:
1. FORMANT DETERMINATIONUses LP (linear prediction) to model vocaltract as cascaded 2nd order digital resonators.External source testing is shown to augmentor replace LP for pathological vowels (Inv).
2. SOURCE MODELINGUses inverse filtering and least squaresoptimization to fit source waveform to astandard model (LF).
NONPERIODIC ANALYSIS:
3. ANALYSIS OF PITCH VARIATIONUses high resolution pitch tracking to measure detailed nonperiodic frequency variation.Variations are segmented into low andhigh frequeny FM with Gaussian form.
ANALYSIS
8
4. FM DEMODULATIONPitch variations are removed from originalvoice to achieve accurate noise estimation(step 7) (Inv.)
5. ANALYSIS OF POWER VARIATIONUses power tracking to measure detailednonperiodic loudness variations.Variations are segmented into low andhigh frequency AM with Gaussian form.
6. AM DEMODULATIONPower variations are removed from originalvoice to achieve accurate noise estimation(step 7) (Inv.)
7. ASPIRATION NOISE Frequency domain methods are used to separate aspiration noise component. Thenoise is spectrally modeled.[Gus de Krom]
ANALYSIS
9
ANALYSIS
COLLECTIONOF VOICESAMPLES
VOICEANALYSIS
PARAMETERS(PITCH, NSR,FORMANTS,..)
VALIDATION
PERCEPTUALCOMPARISONS
+
-
VOICESYNTHESIS
ANALYSIS BY SYNTHESIS
10
ANALYSIS
ANALYSIS/SYNTHESIS MODEL OVERVIEW
SOURCE WAVEFORM
FMMODULATION
AMMODULATION
SPECTRALSHAPING
GAUSSIANNOISE
VOCALTRACT
OUTPUTVOICE
PERIODIC
NONPERIODIC
+
+
SYNTHESIS
ANALYSIS
11
MIC SIGNAL
LPC FORMANTANALYSIS /MANUAL OPS
JITTERESTIMATE.
TREMOR TIME HIST
INVERSEFILTERING
RAW FLOWDERIVATIVE
SRC NOISESPECTRUM
RESAMPLETO REMOVETREMOR
SYNTHESIZER
FORMANTS
FITTED LF SOURCE PULSE
LEAST SQRLF FIT
PITCH TRACKER
CEPSTRALNOISEANALYSIS
NSR ESTIMATE
CONST. PITCHVOICE
PITCH TIME HIST
SHIMMERESTIMATE
VOLUME TIME HIST
POWER TRACKER
POWER TIME HIST
RESAMPLETO REMOVETREMOR
CONST. POWERVOICE
MIKE SIGNAL
ANALYSIS
OVERVIEW OF PROJECT OPERATONS
12
UNKOWN SYSTEM PREDICTOR
u(n) s(n)
s’(n)
+
-
e(n)
∑=
−−p
k
k
k za
G
1
1
∑=
−p
k
k
k z1α
ESTIMATED INVERSE SYSTEM
H(z)
A(z) ≈−= ∑=
−p
k
k
k z1
1 α G/H(z)
LINEAR PREDICTION
(SOURCE)(VOCALTRACT)
Estimates the vocal tract as an all-pole filterby minimizing the error between actual andmodel-predicted signals.
(MODEL)
(ERROR)
PERIODIC ANALYSIS
13
IDEALIZED LP RESULT
0.03 0.035 0.04 0.045 0.05 0.055 0.06
-10
-8
-6
-4
-2
0
2 ERROR SIGNAL OF COVARIANCE LPA = INVERSE FILTERED OUTPUT
0.03 0.035 0.04 0.045 0.05 0.055 0.06-20-15-10-505
10152025 LPC COV. PREDICTOR: LINE = ACTUAL OUT, DOT= PREDICTED
-1.5 -1 -0.5 0 0.5 1 1.5-1
-0.8-0.6-0.4-0.2
00.20.40.60.8
1
Real part
Imag
inar
y pa
rt
LPC COVARIANCE ROOTS. O=TRUE X=LPC
POLE REFLECTEDINSIDE UNIT CIRCLE
Requires a priori knowledge of system.More difficult for pathological vowels.
PERIODIC ANALYSIS
14
SOURCE TIME SERIES VOCAL TRACT TRANSFER FUNCTION
VOICE TIME SERIESVOICE SPECTRUM
SOURCE TIME SERIES VOCAL TRACT TRANSFER FUNCTION
VOICE TIME SERIESVOICE SPECTRUM
SOURCE TIME SERIES VOCAL TRACT TRANSFER FUNCTION
VOICE TIME SERIESVOICE SPECTRUM
CASE 0: NORMAL SOURCE AND NORMAL VOCAL TRACT
CASE 1: “BREATHY” SOURCE AND NORMAL VOCAL TRACT
CASE 2: NORMAL SOURCE AND ABNORMAL VOCAL TRACT
SOURCE-FILTER AMBIGUITYSource & filter are mixed in final voice.Unique LP solution may be difficult.
PERIODIC ANALYSIS
15
≤−+−=≤−=
≤==
−−
−−
ce
tt
eB
ce
tt
e
eg
t
ttttetmEtE
tttEtE
tttEtE
tE
eee
e
e
�
�
),()(
,)(
,sin)(
)()(
2
)(
2
01
ε
ε
α ω
0 0.002 0.004 0.006 0.008 0.01 0.012-150
-100
-50
0
50
100
150
T (SECONDS)
FLO
W U
(t)
& D
ER
IVA
TIV
E E
(t)
E1 (FIRST SEG.) E2 (SECOND SEG.)
U(t)
30*E(t)
tp
(te,Ee)
tc
(t2,Ee/2)
= ∫ E t d t( )
(tpk,Epk)
FITTING RAW SOURCE TO LF Having established the inverse filteredsource, it is fit to the LF model [Qi]
PERIODIC ANALYSIS
16
HIGH RESOLUTION PITCH TRACKING Nonperiodic analysis begins with interpolatingpitch tracking.
NON-PERIODIC ANALYSIS
TIME (SEC)
0.018 0.02 0.022 0.024 0.026 0.028 0.03 0.032 0.034 0.036-8
-6
-4
-2
0
2
4
6
8
VO
ICE
SIG
Measured Period
0 0.2 0.4 0.6 0.8 1255
260
265
270
275
FRE
Q (
HZ
)
TIME (SEC)
VOICE SIGNAL
PITCH TRACK
17
0 0.2 0.4 0.6 0.8 1
260
265
270
275
FRE
Q H
Z
SEC
0 0.2 0.4 0.6 0.8 1
-4
-2
0
2
4
FRE
Q H
Z
SEC
FM DEVIATION SEGREATED TOLOW AND HIGH FREQUENCY
The pitch track is low/hi pass filtered to yield tremor and HFPV (High FrequencyPitch Variation).
NON-PERIODIC ANALYSIS
18
-1.5 -1 -0.5 0 0.5 1 1.50
5
10
15
20
25
30
35
40
45
DELT FREQ (%) TOTSKIP=0 FCUT=10 TOTMAN=0
#OC
CU
RR
AN
CE
S
GAUSSIAN HFPV
Successful pitch tracking yields a Gaussiandistribution in HPFV. The standard deviationis a convenient measure of HFPV.
NON-PERIODIC ANALYSIS
19
FM DEMODULATION
The pitch track may be used to demodulatethe original voice to obtain a version withalmost no pitch variation; re-trackingverifies constant pitch (<0.1%).
NON-PERIODIC ANALYSIS
0 0.2 0.4 0.6 0.8 1
-0.1
-0.05
0
0.05
0.1
DE
LT
A F
RE
Q P
ER
CE
NT
TIME (SEC)
20
0 100 200 300 400 5000
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5x 10
4
SAMPLE NUMBER
SM
OO
TH
ED
AB
S O
RIG
VO
ICE
PITCH TRACK FEATURES
ENVELOPE MINIMA
0 0.5 1 1.5 2 2.5 3 3.5 4x 10 4
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
SAMPLE #
POW
ER
POWER TRACKING
Analogously to pitch tracking, voice poweris tracked.
NON-PERIODIC ANALYSIS
POWER TRACK
21
0 0.2 0.4 0.6 0.8 1
0.5
1
1.5
2 x 10 8 ORIGINAL POWER ( 0) AND TREMOR (LINE)
PO
WE
R
TIME (SEC)
0 0.2 0.4 0.6 0.8 1
-20
-10
0
10
20 SHIM% = 100*(POWER - LOWPASS POWER)/POWER
DE
LT
A P
OW
ER
PE
RC
EN
T
TIME (SEC)
POWER SEGREGATED TOLOW AND HIGH FREQUENCY
The power track is low/hi pass filtered to yield low frequency power variations andhigh frequency shimmer.
NON-PERIODIC ANALYSIS
22
-20 -15 -10 -5 0 5 10 150
5
10
15
20
25
30
35
40
DELT PWR (%)
#OC
CU
RR
AN
CE
S
SHIM% HIST. STAND DEV = 4.823%
GAUSSIAN POWER VARIATIONS
Shimmer also displays Gaussian variations.
NON-PERIODIC ANALYSIS
23
0 0.5 1 1.5 2 2.5 3 3.5 4x 104
0.75
0.8
0.85
0.9
0.95
1VARIOUS MEASURES OF SIGNAL STRENGTH
SAMPLE #
POWER
MAX AMPL.
SUMENERGY
AM DEMODULATION
The power track may be used to demodulatethe original voice to obtain a version withalmost no variation in strength; re-trackingverifies constant power.
NON-PERIODIC ANALYSIS
24
ASPIRATION NOISE ANALYSIS
Aspiration noise is segregated via spectraltechniques. Peaks in the FFT of the log of the FFT (cepstrum) represent periodic energy,and are filtered out with a comb filter (lifter).Results are used to calculate noise-to-signalratio (NSR).
NON-PERIODIC ANALYSIS
0 1000 2000 3000 4000 50000
1
2
3
4
5
6
7
FREQUENCY (HZ)
LO
G10
MA
GN
ITU
DE
Figure 2.30a. PSD oforiginal voice.0 0.1 0.2 0.3 0.4 0.5
0
0.020.04
0.060.080.1
0.12
TIME (SEC)Figure 2.30b. Cepstrum of original voice.
0 0.005 0.01 0.015 0.02
0
0.020.04
0.06
0.080.1
0.12
TIME (SEC)Figure 2.30c. Cepstrum (expanded scale).
0 0.005 0.01 0.015 0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
TIME (SEC)Figure 2.30d. Comb-liftered cepstrum of 14c.
0 1000 2000 3000 4000 5000-2-101234567
FREQUENCY (HZ)
LO
G10
MA
GN
ITU
DE
Figure 2.30e. Orig PSD, aspriation PSD,and vocal tract.
0 1000 2000 3000 4000 50001.5
2
2.5
3
3.5
4
4.5
FREQUENCY (HZ)
LO
G10
MA
GN
ITU
DE
Figure 2.30f. Source aspiration PSD with vocal tract removed and fitted to 25-pointpiecewise-linear model.
25
FM DEMODULATION IMPROVESNSR ACCURACY
Using FM demodulation improves resolutionof spectral peaks of periodic components,thus allowing longer FFT windows and moreaccurate NSR determination.
NON-PERIODIC ANALYSIS
0 100 200 300 400 500 600 700 800
-1
0
1
2
3
4
5
6
7
FREQUENCY (HZ)
LO
G10
MA
GN
ITU
DE
26
0 5 10 15 20 25 30 35
-30
-25
-20
-15
-10
-5
0
NS
R (
DB
)
CASE# - SORTED BY ASCENDING ORIGINAL NSR
CHANGES IN NSR AFTER FM ANDAM DEMODULATION
FM demodulation reduces NSR measuresby up to 20 dB, yielding results closer toperceived levels. AM demodulation has much less effect.
NON-PERIODIC ANALYSIS
ORIG
ALL FM REMOVED
TREMOR REMOVED
27
PC #1: STIMULUS GEN.
STIMULUSSIGNAL
D/A
AMPLIFIER XDUCER
/a/
ACOUSTIC CONDUIT
PC #2: DAQ
SIGNALCONDITIONER
A/D
A/D
MEM.
MICROPHONECH 1
CH 2
SIGNALCONDITIONER
VOCAL TRACT
TUBE OF LENGTH L WITH CLOSED END.FORMANTS AT F = C/4L, 3C/4L, 5C/4L,...
EXTERNAL (ES) SOURCE ANALYSISSource-filter ambiguity may be resolvedby augmenting the glottal source with anknown external stimulus. [Epps].
PERIODIC ANALYSIS
28
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
x 104
-60
-40
-20
0
20
40
60
80
100
120
140SPECTRUM WITH RAG, W/O RAG, & MAG OF T.F. (YEL)
FREQUENCY (Hz)
MA
GN
ITU
DE
(dB
)
|HB(f)|
|HA(f)|
|V(f)|
TUBE FORMANTS
ES VERIFICATION A simple plastic tube model verified theES experimental setup. Resonances occurat expected frequencies.
PERIODIC ANALYSIS
29
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30SPECTRA D1: VC LPA(DASH), VC FFT(SOLID) @ 0dB, EXTSRC TF(DOT) @ 20dB
F1 F2
F3 F4
LPA
FFT
EXT SRC T.F.’S
ES: NORMAL /a/ LP & FFT analysis show consistent results with ES analysis for a normalvowel.
PERIODIC ANALYSIS
30
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30D1BRTHY: VOICE LPA & FFT (BOT), EXTSRC TF (TOP)
FREQUENCY (Hz)
MA
GN
ITU
DE
(dB
)
F1 F2
F3 F4LPA
FFT
EXT SRC T.F.’S
ES: SIMULATED BREATHY /a/ LP & FFT analysis show poor resolutionfor F3 and F4 for a breathy /a/, while theES resolution for F3 and F4 remains good.
PERIODIC ANALYSIS
31
SYNTHESIS
SYNTHESIS OF PATHOLOGICAL VOWELS
Synthesis is a critical step in the study of pathological vowels. It provides evidence of the success of analysis and modeling steps via immediate comparisons of original and synthetic voice.
Two synthesizers were implemented:
1. A realtime hardware-based synthesizer capable of providing instant response to changes in model parameters.
2. A software synthesizer implemented in MATLAB with extended features, convenient graphical interface, and ease of modification.
32
LOWPASSFILT.
CURRENT REALTIME SYNTHESIZER FUNCTIONAL OVERVIEW
D/AAGC
4 ZEROES
. . .
20 POLES
GAH
ASPNOISE
OUTPUTSIGNAL FILE
RECORDWAV
STORE/RECALL CONTROL PARMS
PARAMETER TIME VARIATION
SOURCESELECTION
SOURCE CONTROLS
JITTER SHIMMER DIPLOPHONIA
CLKX86 INTERUPT
AMP
IMPL
KGLOT88
LF1
LF2
ARB
ARBITRARYSOURCEFILE
SPKR
+
SYNTHESIS
REALTIME SYNTHESIZER- Implemented in native X86 assembly
language- Executes all code within 100us cycle- Overrides PC OS to achieve determinancy- Employs dedicated clock, I/O, and controlhardware implemented in a wire-wrap PCB adapter card
33
SYNTHESIS
SYNTHESIS VALIDATION
The current model, analysis tools, and synthesizers yield a high level of fidelity in generation of synthetic pathological vowels.The system is currently employed at the UCLA Voicelab for NIH funded perceptual studies.
In order to objectively validate the analysis/synthesis process, the loop is closed by re-analyzing the synthetic time series to confirm parameter values.
Re-analysis also provides opportunity to observe interactions of nonperiodic components.
34
SYNTHESIS
SYNTHESIS VALIDATION
-30 -25 -20 -15 -10 -5 0-30
-25
-20
-15
-10
-5
0
A.N. SET NSR IN SYNTHESIZER NPB21
ME
AS
UR
ED
NS
R I
N S
YN
TH
ET
IC (
DB
)
Re-measured synthetic aspiration noise level agrees with level set in synthesizer.
35
SYNTHESIS
SYNTHESIS VALIDATION
Aspiration noise adds about %0.2 to HFPVmeasurements.
0 0.5 1 1.5 20
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
JITTER LEVEL SET IN SYNTHESIZER (%)
JIT
TE
R M
EA
SUR
ED
IN
SY
NT
HE
TIC
(%
)
A.N. SET NSR IN SYNTHESIZER (dB)
-30 -25 -20 -15 -10 -5 0-30
-25
-20
-15
-10
-5
0
ME
ASU
RE
D N
SR I
N S
YN
TH
(dB
)
HFPV adds about 4dB to NSR measurements.
36
SYNTHESIS
SYNTHESIS VALIDATION
Subjective analysis by synthesis experiments demonstrate the success of AM and FM demodulation in achieving accurate modeling of nonperiodic features. Listeners adjust syntheticaspiration noise to match original.
Match improves with demodulation
-30 -25 -20 -15 -10 -5 0
-30
-25
-20
-15
-10
-5
0
SA
BS
AS
PIR
AT
ION
NO
ISE
(D
B)
CEPSTRAL NSR (DB)
PEARSON = 0.51
ORIGINAL VOICE (NO DEMOD)
37
SYNTHESIS
SYNTHESIS VALIDATION
-30 -25 -20 -15 -10 -5 0-30
-25
-20
-15
-10
-5
0
SA
BS
ASP
IRA
TIO
N N
OIS
E (
DB
)
CEPSTRAL NSR (DB)
TREMOR REMOVED
PEARSON = 0.71
-30 -25 -20 -15 -10 -5 0-30
-25
-20
-15
-10
-5
0
SA
BS
ASP
IRA
TIO
N N
OIS
E (
DB
)
CEPSTRAL NSR (DB)
ALL AM&FM REMOVED
PEARSON = 0.87
38
SUMMARYCONCLUSION
This study has achieved improved automatic, objective analysis and synthesis of speech within the specialization of pathological vowels. Specific accomplishments include:
- A unique, symmetric model fornonperiodic components as AM, FM and spectrally-shaped aspiration noise
- Improved accuracy of noise analysis via AM & FM demodulation
- Application of ES formant identificationfor pathological vowels.
- Implementation of realtime and offlinespecialized high fidelity vowel synthesizers