Audio file (.wav) being overwritten

I find that if I run the code that the audio file becomes overwritten so I then need to reload the original data into the directory .

What should I do ?

% y= Audio data
% Fs = Sample rate 

% How to read the first "2" seconds 
% samples = [1,2*Fs];
% clear y Fs
% [y,Fs] =audioread(filename,samples);

clear 
clc
speech = ('coch4.wav');
speech2 = speech;
[y,Fs]=audioread(speech2); %don't use wavread or audioread

audiowrite(speech, speech_trimmed, 44100);


% Q1 a)
speechL = speech(:,1); % Should hear "Sometimes I whisper quietly and sometimes I shout very,very loud"
speechR = speech(:,2); % just noise 

disp(Fs);
%Q1 b)

% Q1 c)
n = size(speech); 

% Q1 d) https://au.mathworks.com/matlabcentral/answers/223670-how-can-i-change-the-sampling-frequency-of-audio-signal
Fs4 = Fs/4;
audiowrite(speech,speech_trimmed,Fs4);
[y,Fs4]=audioread(speech);
n2 = size(speech);

Answer 1

[Walter Roberson]

You have

speech = ('coch4.wav');
speech2 = speech;

So your speech2 filename is the same as your speech filename.

[y,Fs]=audioread(speech2); %don't use wavread or audioread

So you read from coch4.wav via speech2 filename

audiowrite(speech, speech_trimmed, 44100);

and then you write to the file name given by speech, which is the same as the filename given by speech2, so you are writing to the same file that you read the data from.

[LearningMatLab]

So what should I write instead ?

[Walter Roberson]

% y= Audio data
% Fs = Sample rate 
% How to read the first "2" seconds 
% samples = [1,2*Fs];

speechfile_in = 'coch4.wav';
speechfile_out = 'choc4_2sec.wav';
speechfile_out2 = 'choc4_slower.wav';

[y, Fs] = audioread(speechfile_in);
audiowrite(speechfile_out, speech_trimmed, 44100);
% Q1 a)

speechL = speech(:,1); % Should hear "Sometimes I whisper quietly and sometimes I shout very,very loud"
sound(speechL, Fs);
speechR = speech(:,2); % just noise
sound(speechR, Fs);
disp(Fs);
%Q1 b)
% Q1 c)
n = size(speech); 
% Q1 d) https://au.mathworks.com/matlabcentral/answers/223670-how-can-i-change-the-sampling-frequency-of-audio-signal
Fs4 = Fs/4;
audiowrite(speechfile_out2, speech_trimmed, Fs4);
[y, Fs4] = audioread(speech);
n2 = size(speech);
sound(speech, Fs4);

[Walter Roberson]

Warning: this code does not attempt to implement the "2 seconds" that is in the comments.

[LearningMatLab]

So 'choc4_2sec.wav' and 'choc4_slower.wav' are audio files that become created from the audiowrite() ?

[Walter Roberson]

Yes.