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MATLAB Functionality for Digital
Speech Processing
• MATLAB Speech Processing Code
• MATLAB GUI Implementations
1Lecture_3_2012

Basic Functionality
• read a speech file (i.e., open a .wav speech file and read the speech sample into a
MATLAB array)
• write a speech file (i.e., write a MATLAB array of speech samples into a .wav
speech file)
• play a MATLAB array of speech samples as an audio file
• play a sequence of MATLAB arrays of speech samples as a sequence of audio files
• record a speech file into a MATLAB array
• plot a speech file (MATLAB array) as a waveform using a strips plot format
• plot a speech file (MATLAB array) as one or more 4‐line plot(s)
• convert the sampling rate associated with a speech file (MATLAB array) to a
different sampling rate
• highpass filter a speech file (MATLAB array) to eliminate hum and low frequency
noise
• plot a frame of speech and its associated spectral log magnitude
• plot a spectrogram of a speech file (MATLAB array)
• plot multiple spectrograms of one or more speech files (MATLAB arrays)
2

Read a Speech File into a MATLAB
Array
• [xin, fs, nbits] = wavread(filename);
• [xin, fs] = loadwav(filename);
– filename is ascii text for a .wav‐encoded file which contains a speech
signal encoded using a 16‐bit integer format
– xin is the MATLAB array in which the speech samples are stored (in
double precision format)
– fs is the sampling rate of the input speech signal
– nbits is the number of bits in which each speech sample is encoded
(16 in most cases)
– program wavread scales the speech array, xin, to range −1≤xin≤1,
whereas loadwav preserves sample values of the speech file and
hence array xin is scaled to range −32768≤xin≤32767
• [xin1, fs, nbits] = wavread(‘s5.wav’);
• [xin2, fs] = loadwav(‘s5.wav’);
3

Read a Speech File into a MATLAB Array
• % test_wavread.m
• % test waveread function
• %
• % read speech samples from file 'test_16k.wav' into array x1 using wavread
• % routine
• filein='test_16k.wav';
• [x1,fs1,nbits]=wavread(filein);
•
• % print out values of fs1, nbits, wavmin1, wavmax1
• wavmin1=min(x1);
• wavmax1=max(x1);
• fprintf('file: %s, wavmin/wavmax: %6.2f %6.2f, fs1: %d, nbits: %d n‘,…
• filein,wavmin1,wavmax1,fs1,nbits);
•
• % read speech samples from same file into array x2 using loadwav routine
• [x2,fs2]=loadwav(filein);
•
• % print out values of fs2, nbits, wavmin2, wavmax2
• wavmin2=min(x2);
• wavmax2=max(x2);
• fprintf('file: %s, wavmin/wavmax: %d %d, fs2: %d n',...
• filein,wavmin2,wavmax2,fs2);
Terminal Display:
file: test_16k.wav, wavmin/wavmax: ‐1.00 1.00, fs1: 16000, nbits: 16
file: test_16k.wav, wavmin/wavmax: ‐32768 32767, fs2: 16000 4

Play/Plot Existing Speech File
• Play_Plot_Speech_GUI25.m
– MATLAB GUI for basic operations of reading in a
file, playing the speech array, and plotting the
speech waveform
8

Write a Speech Array into a Speech
File
• wavwrite(xout, fs, nbits, filename);
• savewav(xout, filename, fs);
– xout is the MATLAB array in which the speech samples are stored
– fs is the sampling rate of the output speech signal
– nbits is the number of bits in which each speech sample is encoded
– filename is the ascii text for the .wav‐encoded file in which the
MATLAB signal array is to be stored
– for wavwrite the MATLAB array xout needs to be scaled to the range
−1≤xin≤1 whereas for savewav the MATLAB array xout needs to be
scaled to the range −32768≤xout≤32767
• wavwrite(xin1, fs, ‘s5out.1.wav’);
• savewav(xin2, ‘s5out.2.wav’, fs);
9

Write a Speech Array into a Speech File
• % write out array x1 into speech file using wavwrite routine
• wavwrite(x1,fs1,nbits,'file1out.wav');
• % write out array x2 into speech file using savewav routine
• savewav(x2,'file2out.wav',fs2);
file1out.wav
file2out.wav
10

Play a Speech File
• sound(x, fs);
• soundsc(x, fs);
– for sound the speech array, x, must be scaled to the range
−1≤x≤1
– for soundsc any scaling of the speech array can be used
– fs is the sampling rate f the speech signal
• [xin, fs] = loadwav(‘s5.wav’); % load speech from s5.wav;
• xinn = xin/abs(max(xin)); % normalize to range of − 1 to 1;
• sound(xinn, fs); % play out normalized speech file;
• soundsc(xin, fs); % play out unnormalized speech file;
11

Play Multiple Speech Files
• play_multiple_files.m;
– sequence of filenames read in via filelist, keyboard or file
search
• Example of usage to play out 3 speech files in
sequence:
– kbe=filename entry via filelist(2), keyboard(1), or file
search(0):1; % keyboard chosen
– N=number of files to be played in a group:3; % play out 3
files
– i=1; filename: s1.wav;
– i=2; filename: s2.wav;
– i=3; filename: s3.wav
12

Play Multiple Speech Files
• test_play_files.m
– play the following sequence of files:
Maple_short.wav
s1.wav
beep.wav
test_16k.wav
beep.wav
s2.wav
13

Record Speech into MATLAB Array
• record_speech.m (calls MATLAB function
wavrecord.m)
• function y=record_speech(fs, nsec);
– fs: sampling frequency
– nsec: number of seconds of recording
– y: speech samples array normalized to peak of
32767
14

Record Speech into MATLAB Array
• record_display_speech_GUI25.m
15

Plot Speech Using Strips Plot
16

Plot Speech Using Strips Plot
• strips_plot_GUI25.m
17

Plot Speech Using 4‐Line Plot
18

Sample Rate Conversion
• y = srconv(x, fsin, fsout);
– x: input speech array;
– fsin: input speech sampling rate;
– fsout: desired speech sampling rate;
• Example:
– [xin, fsin] = loadwav(‘s5.wav’); % fsin=8000;
– fsout = 10000; % desired sampling rate;
– y = srconv(xin, fsin, fsout);
19

Sample Rate Conversion
• SRC_GUI25.m
20

Filter Speech Waveform
• filter_GUI25.m
22

Plot Signal and STFT Log Magnitude
23

Multiple Spectra GUI
• multiple_spectra_GUI25.m
24

Plot Spectrogram
• spectrogram_GUI25.m
26

Plot Multiple Spectrograms
27

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