HCS / ACN 6389 Speech Perception Lab

14 Pages·2017·0.7 MB·English

Course Requirements
HCS / ACN 6389
Matlab problems & lab assignments (40%)
Speech Perception Lab 
Oral presentations (10%)

Term project paper (50%)

Dr. Peter Assmann
Fall 2018
Dates for lab assignments Term project: important dates
Lab assignment 1: due Sept 13 Sep 6: Submit project topics (title only)
Lab assignment 2: due Oct 11 Sep 20: Submit project outline
Lab assignment 3: due Nov 1 Sep 27: Present project idea in class
Lab assignment 4: due Nov 29 Nov 29 / Dec 8: Project presentations
• 3-4 page written reports (code + results) on Dec 13: Final project paper due
lab assignments
Homework assignment Matlab
First-time Matlab users: Variables are defined as matrices
 
Complete the interactive MATLAB Tutorial Scalars: 1 x 1
 
https://www.mathworks.com/help/matlab/getting-  Vectors: Row (nx 1) and column (1 x m)
started-with-matlab.html
Matrices: nx m

Matlab Onramp (free 2-hour online Matlab course)
Matlab online (requires login)

Speech signals are represented as vectors
https://matlab.mathworks.com/
 (i.e., as a row or column of numbers).
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Starting with Matlab Starting with Matlab
Command Window – enter commands at Get help!
 
the prompt >> >> help help
Create some numeric variables:

help Display help text in Command Window.
help, by itself, lists all primary help topics. Each primary topic
>> x = 5; % 1x1 scalar corresponds to a folder name on the MATLAB search path.
>> y = 1:12; % 1x12 vector
>> doc Matlab
>> z = rand ( 4, 4 ); % 4x4 matrix
doc Displays help in Matlab’sBrowser Window.
More detailed information is provided.
Starting with Matlab Starting with Matlab
Try this: Create character variables by enclosing
 
>> help plot text in single quotes:
>> a = 'c'; % 1x1 character
>> b = dir( '*.m'); % directory listing
Starting with Matlab Starting with Matlab
Create character variables by enclosing Colon (:) operator
 
text in single quotes: >> x = 1 : 10; % create vector [1,2,3,…,10]
>> x = 1 : 1 : 10; % same as above
>> a = 'c'; % 1x1 character
>> x = 1 : 2 : 10; % 1,3,5,…,10
>> b = dir( '*.m'); % directory listing
>> x = 0 : 0.5 : 2; % [0,0.5,1,1.5,2]
The semicolon tells Matlab not to echo the
contents of the variable on the screen.
This is important for large vectors
(e.g. 10 seconds of speech). >> help :
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Starting with Matlab Starting with Matlab
Concatenate variables [make a list] Concatenate variables [make a list]
 
>> a = [1 2 3 4 5]; % row vector >> a = [1; 2; 3; 4; 5]; % column vector
>> b = [100 -5 0]; >> b = [100; -5; 0]; % uses semi-colon
>> c = [a b]; >> c = [a; b];
>> disp(c)
Numeric variables
c =
1 2 3 4 5 100 -5 0
Starting with Matlab Starting with Matlab
Concatenate variables (make a list) Concatenate variables (make a list)
 
Be careful not to concatenate a row vector

>> a = 'Matlab is fun! '; Character variables with a column vector!
>> b = 'Speech perception is interesting.';
>> a = [1 2 3 4 5];
>> c = [a b];
>> b = [100; -5; 0];
>> disp(c)
>> c = [a b];
c =
Error: Dimensions of arrays being concatenated are not consistent.
Matlab is fun! Speech perception is interesting.
Starting with Matlab Starting with Matlab
Workspace – repository for variables you Workspace – repository for variables you
 
have created or loaded. Variables may be have created or loaded. Variables may be
viewed, manipulated, saved, or cleared. viewed, manipulated, saved, or cleared.
List the variables in the workspace: List the variables in the workspace:
 
>> who >> whos
Name Size Bytes Class Attributes
Your variables are:
a 1x10 80 double
ans 1x10 20 char
a ans b c
b 1x4 32 double
c 1x14 112 double
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Starting with Matlab Starting with Matlab
Clear the workspace when you start a new Save your results:
 
script.
>> clear % Save all variables from the workspace to test.mat:
>> save test.mat
% Save selected variables from the workspace to test.mat:
>> save('test.mat', 'a', 'b');
Starting with Matlab Exercise
 Load Matlab data from a file: 1. Create a row vector awith integers from 1 to 
100.
% Load all variables from file test.matinto the workspace : 2. Create another row vector bwith integers 
>> load test.mat from 5 to 95 in  steps of 5.
3. Concatenate aand band store it as a third 
% Load selected variables from test.mat:
vector, c.
>> load('test.mat', 'a', 'b');
4. Plot the vector c. 
5. Put the commands into a script and save it in 
a Matlab script, exercise1.m. 
Starting Matlab Starting Matlab
Matlab opens in a specific directory Use “cd <path>” to change to another

(folder) on your computer, allowing you to directory:
load or save files without specifying a >> cd C:\Users\assmann\Documents
path.
Type “cd” to find the current directory
 Be careful to distinguish forward slash (/) from backslash (\)
Use the cd command to change to another --these differ depending on the operating system

directory
>> cd ( 'your\new\directory\' )
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Digital representations of speech
Digital representations of signals
Speech waveform: representation of the

amplitude variations in the signal as a function
 of time.
 x 104
• Amplitude
quantization 2
amplitude time •• ITs(n8aim 0mt0hpe0el esesa axrmamatmepp llpieislns e8/g,s t)kh H e z Amplitude 01
with 16-bitamplitude -1
quantization.
sampling quantization -2
0 200 400 600 800
Time (ms)
Digital representations of signals Vector representation of speech
Sampling frequency (e.g. 44.1 kHz) >> [y, fs]=audioread('wheel.wav'); % load waveform

(cid:0)
Nyquist frequency
Effects of discrete-time sampling on bandwidth  audioread.mis a Matlab function to read data from
 (cid:0)(cid:0) .wav files
Quantization rate (16 bits)
  Left side = output variables; right side = input variables
(cid:0)16 bits =216 quantization steps  The variable ‘y’ contains the speech signal.
(cid:0)Effects of discrete-level quantization on dynamic range  The variable ‘fs’ contains the sample rate in Hz.
Exercise Exercise
 Create a script, exercise2.mto load and plot a   Display the sample rate 
waveform file.   Compute the size of the waveform vector y
 Download (or record) a .wav file and put it in   Plot the waveform
the current directory:
 Play the waveform using the soundsccommand
 https://www.utdallas.edu/~assmann/hcs6389/scripts_functions.html
 Right click on wheel.wav
>> [y, fs]=audioread('wheel.wav'); 
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Vector representation of speech Annotating plots
 Load the waveform and plot it:
 >> [y,fs]=audioread('wheel.wav'); % load  >> axis( [ 0 400 -1 1 ] ); % set axis limits
waveform  >> xlabel('Time (ms)'); % x-axis label
 >> t=(1:length(y) ) ./ (fs/1000); % set up time  >> ylabel('Amplitude'); % y-axis label
axis in milliseconds  >> title('Waveform plot'); % axis title
 >> plot( t, y ); % use plot command
 Time (x) axis in milliseconds (1000 ms = 1 second)
 Amplitude (y) axis ~ sound pressure level quantized
 to 16 bits and range set to ±1.
Exercise
Try this:
>> axis tight
>> axis auto
 Use built-in Matlab functions to find various
properties of the waveform:
» length ( y ) % vector length
» min ( y ) % minimum value
» max ( y ) % maximum value
» mean ( y ) % mean value
» std ( y ) % standard deviation
» plot ( y ) % plot waveform
» sound ( y, fs ) % listen to waveform
» soundsc( y, fs ) % “safe” version of sound 21
Fourier analysis and synthesis
• D.P.W. Ellis (2009). An introduction to signal 
processing for speech. In The Handbook of 
Phonetic Science, , 2ndedition, edited by 
Hardcastle, Laver, and Gibbon. chapter 22, pp. 
757‐780, Blackwell.
Ellis (2009, p. 12)
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Spectral analysis
Frequency domain representation
 Amplitudespectrum: sound pressure levels  Why perform spectral analyses of speech?
associated with different frequency  The ear+brain carry out a form of frequency analysis
components of a signal  The relevant features of speech are more readily
visible in the amplitude spectrum than in the raw
Power or intensity waveform
Amplitude or magnitude  BUT: the ear is not a Fourier analyzer.
Log units and decibels (dB)  Fourier analysis provides amplitudeand phase
spectrum; speech cues have been mainly associated
Phasespectrum: relative phases associated
 with the amplitude spectrum. However, the ear is not
with different frequency components "phase-deaf"; many phase changes are clearly
audible.
Degrees or radians  Frequency selectivity is greatest for frequencies
below 1 kHz and declines at higher frequencies
Spectral analysis in Matlab
 Amplitude spectrum of a vector:
» X= fft (y);
» help fft
FFT Discrete Fourier transform.
FFT(X) is the discrete Fourier transform (DFT) of vector
X. If the length of X is a power of two, a fast radix-2 fast-
Fourier transform algorithm is used. If the length of X is
not a power of two, a slower non-power-of-two algorithm
is employed. For matrices, the FFT operation is applied to
each column.
FFT(X,N) is the N-point FFT, padded with zeros if X has less
than N points and truncated if it has more.
Spectral analysis in Matlab Spectral analysis in Matlab
Log magnitude (amplitude) spectrum: Log magnitude (amplitude) spectrum:
 
» X= fft (y); » plot(20*log10(abs(fft(y))))
» m = 20 * log10 ( abs ( X ) );
140
» help abs
120
100
ABS Absolute value.
80
ABS(X) is the absolute value of the elements of
X. When X is complex, ABS(X) is the complex 60
modulus (magnitude) of the elements of X.
400 200 400 600 800 1000
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Plotting amplitude spectra Plotting amplitude spectra
» help fp » [a,f]=fp(wave,n,rate,string,window);
»[a,f]=fp(y,1000,rate,'speech','hann');
FP: function to compute & plot amplitude spectrum
Usage: [a,f]=fp(wave,n,rate,string,window); speech
20
wave: input waveform
10
n: if unspecified, n=length(wave); padded with zeros if
0
rstanrteienc:g ess:a stmaitrplyel ef orar tger ianp hH (zd (edfeafualut lnt o1n0e0)00 Hz) mplitude (dB)--2100
A-30
windowoptions: 'hann', 'hamm', 'kais', or 'rect'
-40
(default=hanning)
[a,f]:FFT log magnitude, frequency -500 1 Frequen2cy (kHz) 3 4
Speech spectrograms
Speech spectrogram
 What is a speech spectrogram?
 Display of amplitude spectrum at successive instants in  running amplitude spectra (codes amplitude
time ("running spectra") changes in different frequency bands over time).
 How can 3 dimensions be represented on a two-
dimensional display?
 Gray-scale spectrogram
 Waterfall plots
 Animation
 Why are speech spectrograms useful?
 Shows dynamic properties of speech
 Includes frequency analysis
“The watchdog”
Speech spectrograms in Matlab
waveform
spectrogram
» help specgram
SPECGRAM Calculate spectrogram from signal.
B = SPECGRAM(A,NFFT,Fs,WINDOW,NOVERLAP)
calculates the spectrogram for the signal in vector A.
SPECGRAM splits the signal into overlapping
segments, windows each with the WINDOW vector
and forms the columns of B with their zero-padded,
length NFFT discrete Fourier transforms.
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Speech spectrograms in Matlab
» help sp
sp: create gray-scale spectrogram
Usage: h=sp(wave,rate,nfft,nsampf,nhop,pre,drng);
wave: input waveform
rate: sample rate in Hz (default 8000 Hz)
nfft: FFT window length (default: 256 samples)
nsampf: number of samples per frame (default: 60)
nhop: number of samples to hop to next frame
(default: 5 samples)
pre: preemphasis factor (0-1) (default: 1)
drng: dynamic range in dB (default: 80)
title: title for graph (default: none)
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