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Under guidance of Dr. G. PradhanNIT PATNA (ECE dept.)
Presented by -Kamlesh Kalvaniya -(1104080)Niranjan Kumar –(1104087)Piyush Kumar-(1104091)B.TECH 4th yr (ECE dept.)N.I.T. PATNA ECE, DEPTT.
SPEAKER RECOGNITION UNDER LIMITED DATA CONDITION
1. Introduction 2. Baseline speaker verification system3. Future Plan
OUTLINE
Speaker Recognition is the computing task of validating identity claim of a person
from his/her voice.
Applications:- Authentication Forensic test Security system ATM Security Key Personalized user interface Multi speaker tracking Surveillance
Introduction
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Identification v/s verification
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Phase of Speaker Verification• Enrollment Session or Training Phase• Operating Session or Testing Phase
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Training & Testing Phase
Training Reference model
Speech
Identity claim
Testing
Speech R
Accept/reject
Pre-
processing
Feature
extraction
Model
Building
Pre-
processing
Feature
extraction
comparison
Decision logic
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PreprocessingPreprocessing is an important step in a speaker verification system. This also called voice activity detection (VAD).
VAD separates speech region from non-speech regions[2-3] It is very difficult to implement a VAD algorithm which works consistently for
different type of data VAD algorithms can be classified in two groups
Feature based approach Statistical model based approach
Each of the VAD method have its own merits and demerits depending on accuracy, complexity etc.
Due to simplicity most of the speaker verification systems use signal energy for VAD.
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The speech signal along with speaker information contains many other redundant information like recording sensor, channel, environment etc.The speaker specific information in the speech signal[2] Unique speech production system Physiological Behavioral aspects
Feature extraction module transforms speech to a set of feature vectors of reduce dimensions To enhance speaker specific information Suppress redundant information.
Feature Extraction
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• Robust against noise and distortion• Occur frequently and naturally in speech• Be easy to measure from speech signal• Be difficult to impersonate/mimic• Not be affected by the speaker’s health or long term variations in voice
Selection of Features
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Types Of Features
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Feature Extraction Techniques
A wide range of approaches may be used to parametrically represent the speech signal to be used in the speaker recognition activity. Linear Prediction Coding Linear Predictive Ceptral Coefficients Mel Frequency Ceptral Coefficients Perceptual Linear Prediction Neural Predictive Coding
Most of the state-of-the-art speaker verification systems use Mel-frequency Cepstral Coefficient (MFCC) appended to it’s first and second order derivative as the feature vectors
Easy to extract Provides best performance compared to other features MFCC mostly contains information about the resonance structure of the vocal tract
system
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1. Analog to digital conversion 2. Pre emphasis 3. Framing & windowing4. Fast Fourier Transform5. Mel scale wrapping6. MFCC
MEL FREQUENCY CEPTRAL COEFFICIENTS
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MFCC
Step 1:- Analog to digital conversion: is transformed to digital form by sampling it at given frequency.
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MFCC
Step 2:- Pre-emphasis: The amount of energy present in the high frequency (important for speech) are boosted.
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MFCC
Step 3:(framing)the signal is divided into frames of given size.
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MFCC FRAMING
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MFCC FRAMING
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MFCC FRAMING
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MFCC FRAMING
25ms
10 ms
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MFCC WINDOWING
• The next step is to window individual frame to minimize the signal discontinuities at the beginning and end of each frame.
• The concept applied here is to minimize the spectral distortion by using the window to taper the signal to zero at the beginning and end of each frame.
• We have used hamming window
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MFCC
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MFCC
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MEL FILTERBANK
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MFCC
DCT
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MFCC
DCT
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Speaker Modelling
• Vector Quantization• Gaussian Mixture Model• Gaussian Mixture Model-UBM• Hidden Markov Model• Artificial Neural Networks• Super Vector Machines• I-Vector
Gaussian model assumes the feature vectors follow a Gaussian distribution, characterized by mean vectors, covariance matrix and weights
The data unseen in the training which appear in the test data will trigger a low score
Speaker models the statistical information present in the feature vectors it enhances the speaker information and suppress the redundant information
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A Gaussian mixture density defined as-
A Gaussian function for D dimension is defined as-
where- Unimodal Gaussian D=8,16,32,64
ʎ i = {wi , ∑i µi }
wi = Weight
µi = Mean ;
∑i = Covariance ;
i-No. of models(M=356)N.I.T. PATNA ECE, DEPTT.
Gaussian Mixture Model
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For a sequence of T training vector X={x1 , x2 ,…, xT } the GMM likelihood can be defined as-
For estimation of speaker specific GMM, Expectation maximization algorithm is used .
MAXIMUM LIKLIHOOD PARAMETER ESTIMATION
30
ʎtarget : X(MFCC(TESTING DATA)) is from the hypothesized
speaker S ʎUBM : X(MFCC(TESTING DATA)) is not from the
hypothesized speaker S The likelihood ratio test is given by- LR(X)=
The probability of alternative hypothesis P(X/ʎUBM ) =F( P(X/ʎ1), P(X/ʎ2),..., P(X/ʎM))
F( ) is function such as average or maximum of likelihood value of Background Speaker set ( P(X/ʎi) ) .04/15/2023 N.I.T. PATNA ECE, DEPTT.
GMM UBM
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Score Normalisation Where- s- Original Score = log(LR(X)); µI - Estimated mean of s
σI -standard deviation of s
Score Normalisation
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PERFORMANCE EVALUATION NIST has conducted speaker recognition
benchmarking activity on annual basis since 1997.
NIST has provided speech files as development data.
NIST 2003 data- Testing Speech Data-2559 Train Speech Data-356 UBM Female Speech data-251 UBM male Speech data-251
For Baseline speaker verification the following parameter are used VAD: Energy based VAD (0.6 * average
energy) Feature vector: 13 dimension MFCC appended with
delta and delta-delta Modeling: GMM GMM size: 8, 16, 32, 64.0Comparison: log Likelihood score
Development of BASELINE SPEAKER VERIFICATION SYSTEM
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. Flowchart Of Baseline Speaker Recognition System
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DET PLOTFOR TEST
15 SecAND
TRAIN15 SEC
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DET PLOTFOR TEST FULLAND
TRAIN15 SEC
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DET PLOTFOR TEST
15 SecAND
TRAINFULL
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DET PLOTFOR TEST FULLAND
TRAINFULL
Comparison of training data model with Equal Error Rate
.
GAUSSIAN SIZE
8
16
32
64
TEST 15 SecTRAIN 15 SEC
Test FullTrain 15 sec
TEST 15 secTrain Full
Test FullTrain Full
EQUAL ERROR RATE(%)
EQUAL ERROR RATE(%)
EQUAL ERROR RATE(%)
EQUAL ERROR RATE(%)
34.90 34.24 33.18 27.70
33.05 32.28 30.50 25.67
32.46 32.94 28.78 23.67
32.82 33.06 27.42 22.05
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Conclusion
Performance is more sensitive to training data.
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Future Plan
Synthetically generating training and testing speech from limited speech data.
Validating the results on state-of-the-art i-vector based speaker verification system.
Thank you