manually creating my own audio file

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Williah 2018-1-26

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https://ww2.mathworks.cn/matlabcentral/answers/379217-manually-creating-my-own-audio-file

编辑： Walter Roberson 2018-1-28

I followed the instructions in MATLAB website audiowrite, to create an audio wav file. https://www.mathworks.com/help/matlab/ref/audiowrite.html#btjqac7-4

I imported handel.mat etc., and played it back perfectly with, sound(y,Fs);

I then did the same thing for a short music wav file I have, a recording of an E tone simulation of a guitar string, and it played back perfectly as well.

So now I thought I could manually create an array that would create the same sound. I create a short program to create a 44100x2 array so that I would have one second of sound. I displayed the first few rows of the y array I created from the E tone.wav file, "([y,Fs] = audioread('E tone.wav');", used the first value in the array as my data value. This was 9.1553e-05. I alternated between - and + values for each row, as seen in the original wav file

So now I have a 44100x2 array of 9.1553e-05 and -9.1553e-05.

When I use "sound" to play it, I get no sound.

I've review many pages online trying to find out what's going on, but I can't figure out what I'm missing, not seeing.

A chose a different value within the working audio matrix and still nothing.

Does any see what I'm missing?

All help appreciated.

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Stephen23 2018-1-26

编辑：Jan 2018-1-26

在 MATLAB Online 中打开

Williah's "Answer" moved here:

Sure. FYI, I am just learning MATLAB so my code was rough and inefficient, but affective for what I'm trying to do.

Here's what I did as commands (excuse my syntax, not sure proper format for posting commands & code):

>> clear
>> [y,Fs]=audioread('e note.wav');
>> sound(y,Fs)
>> y(1:5,1:2)
ans =
     1.0e-03 *
     -0.0305    0.0305
      0.0916   -0.0305
     -0.1221    0.0305
      0.1221   -0.0610
     -0.1526    0.0305
>> x=ones(44100,2);
>> z=thehardway3(x);
k =
         44100           2
>> z(1:5,1:2)
ans =
     1.0e-03 *
      0.1221    0.1221
     -0.1221   -0.1221
      0.1221    0.1221
     -0.1221   -0.1221
      0.1221    0.1221
>>

And Here's the code:

function [x] = thehardway(y)
k=size(y)
for j=1:2
for i=(1:k(1,1))
    if mod(i,2)==0
        y(i,j) = y(i,j)*(-1)*(.0001221);
    end
    if mod(i,2)~=0
        y(i,j) = y(i,j)*(.0001221);
    end    
end
x=y;
end

I didn't expect an e tone, just noise, but I get nothing, silence. I thought perhaps its in varying the data values, but shouldn't this single values give me at least a noise?

Jan 2018-1-26

编辑：Jan 2018-1-26

@Williah: I've formatted your code. You can do this by your own, see http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup#answer_18099

You have posted the code of "thehardway", but call "thehardway3".

Williah 2018-1-27

Thanks for the formatting. I saved the file thehardway3.m, so accessing is fine. I just named it wrong within. Corrected.

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Answer 1

Jan 2018-1-26

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/379217-manually-creating-my-own-audio-file#answer_301989

编辑：Jan 2018-1-26

在 MATLAB Online 中打开

The code can be simplified:

function x = thehardway(y)
x = repmat(0.0001221, size(y));
x(2:2:end, :) = -x(2:2:end, :);
end

You could here this, if you increase the volume by the factor 1000:

sound(x * 1000);

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Jan 2018-1-28

编辑：Jan 2018-1-28

Williah's comment moved here (please post comments in the section for comments, not as an answer. Stephen has moved two other comments of you already):

Thanks for the code rewrite, much more efficient (and informative :) ).

Interesting result. When I used sound, multiplying by 1000, I hear 2 pops, like electric sparks. I'm going to play with the data values to see what I learn.

One more question. What does the data, 0.1221*e-03, represent? What is the unit of measurement of this data?

Jan 2018-1-28

@Williah: I have no idea, what 0.0001221 represents. I've taken it from your code example. There is no unit for these data. For data of type double, sounds use a range of [-1.0, +1.0]. For a physical meaning, you have to consider the amplifier and speakers.

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