how to extract data from a sound file and do calculations with the data?

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Passband Modulation
I have a sound file named “message.txt” containing the waveform of a voice message embedded in a sinusoid with frequency of 220 Hz, and the sampling frequency is 22000 Hz.
file content consisting of 65120 rows of item as following shows
file source: http://www.2shared.com/document/LCmLelLW/message.html
load the file, and the speech heard
load message.txt
soundsc(message, 22000)
Now what I want to do is do some mathematical calculations of these data.
where r[k] corresponds to message. say for example: r[k] corresponds to the floating point number in first row of the file for k=0. r[k] corresponds to the floating point number in second row of the file for k=1. r[k] corresponds to the floating point number in third row of the file for k=2. and so on. finally, r[k] corresponds to the floating point number in last row of the file for k=65119.
(the lenght of the message/signal length is 65120, obtained using length(message))
how to do that? does anyone get what i mean?
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Walter Roberson
Walter Roberson 2012-10-5
I am not sure what you mean about r[k] ?
Once you have loaded the data into the array "message" it will just be a numeric array and you can do any mathematical processing you want on it.
Passband Modulation
Passband Modulation 2012-10-5
r[k] corresponds to file massage. Say, r[k] corresponds to the floating point number in first row of the file for k=1.
i really dun know how to do the mathematical processing with matlab, could u write down the code? (plz note sin(3.6k) should be in degree)

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Walter Roberson
Walter Roberson 2012-10-5
sum( message .* sind(3.6 * (0:length(message)-1))
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