Why standard Waveform from audio out gets distorted when i reduce the amplitude?

In my attempt to generate a standard sine wave out of a sound card, i started using matlab which has a function soundsc for scaling the output

 t = 0:1/48000:10;
 y = sin(1000*2*pi*t);
 soundsc(y,48000,[a b]);

its ok when my a and b are -1 and 1 respectively, when i try to make them even -0.9 and 0.9 respectively the standard sine wave of 1Khz gets distorted why so ?

are our sound cards will not be able to handle standard sounds ??

Answer 1

[Dinesh Iyer]

Shyam,

The reason for this distortion is that some of the signal values are being clipped. When you specify [a, b], it is assumed that signal you are attempting to playback has values in the range [a, b] and it allows you to scale it to the the range [-1, 1].

In your case, the signal "y" has values in the range [-1, 1] and by specifying [a, b] t be [-0.9 0.9], the values between [-0.9 0.9] in "y" are being scaled to [-1 1]. Values greater than 0.9 are scaled out of range and hence clipped.

The help for the soundsc function makes this clear.

Dinesh

[shyam]

thanks i understood,but i have tried with some other experiment like replacing the y=sin(..) line with y = 0.5 sine(..) but the output was not halved but its response was not linear what may be the problem ?

[Dinesh Iyer]

I am not sure I understand your question.