Plot a sound to get sine waves

Hey, I have a project where I'm trying to plot a sound and show how you can see the sine waves in it. I try with

>> [y,fs]=wavread('C:\Users\Moen\Documents\MATLAB\Sine_wave_440.wav');

>> t=[1/fs:1/fs:length(y)/fs];

>> plot(t,y)

in MATLAB, but all i get in the plot is a blue square. What can I do to show sine waves in a sound?

Thanks!

Answer 1

[Chad Greene]

Can you upload the wave file? Without having the data it's hard to guess, but perhaps you're seeing too many sine waves squished into the window. If t is in seconds, two 440 Hz sine waves should be evident if you type

xlim([0 2/440])

Answer 2

[Star Strider]

The blue square is actually the signal, but plotted so densely you can’t see any detail. (This is normal.) If you want to see the signal in more detail, use the axis function. In your situation, you might want to do something like this:

plot(t,y)
axis([0  100    ylim])

Change the ‘0’ and ‘100’ values as necessary to whatever lets you see the part of the signal you want. (You can also zoom in the figure window, depending on what you want to do, but that is likely not as useful as axis.)

Answer 3

[Leif Olav Moen]

Thanks for the help! xlim([0 2/440]) worked.