Why while using sound function in matlab sound has noise in it?

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Mubasher
Mubasher 2012-5-15
I have modulated and demodulated a sound file and i have bit error rate of zero. Then why output sound is distorted?
clear; clc;
M=2;
freq_sep=100;
nsamp=6;
sampling_frequency=1000;
[data,Fs]=wavread('Pakistan','native');
b=uint8(data);
data_bin=de2bi(b);
fsk_mod=fskmod(data_bin,M,freq_sep,nsamp,sampling_frequency);
noise=awgn(fsk_mod,25);
fsk_demod=fskdemod(noise,M,freq_sep,nsamp,sampling_frequency);
[num,rate]=biterr(data_bin,fsk_demod)
z=bi2de(fsk_demod);
sound(z,Fs)
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Mubasher
Mubasher 2012-5-16
it gives this error
??? Error using ==> sound at 55
Audio data must be real and double-precision.

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Walter Roberson
Walter Roberson 2012-5-15
Possibly the original data was more than 8 bit. What does class(data) show ?
Also, you did not force de2bi() to use 8 bit output per sample.
Is fsk_demod definitely an array and not a vector?
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Walter Roberson
Walter Roberson 2012-5-16
I'm not sure why you say there should be a click? There is nothing special about 0 -- it doesn't mean "turn off the speaker" for example.
Daniel Shub
Daniel Shub 2012-5-16
The soundcard will attempt to produce one voltage for every sample with a value of 0 and another for voltage (its maximum voltage) for every sample with a value greater than 1. I am assuming the number of samples with a value of 0 is small. Periods where the soundcard output is pinned to the maximum will be perceived as silence. The transition from the maximum voltage to the voltage corresponding to the 0-valued samples will be perceived as a click.
maximum voltage with brief periods of significantly smaller voltages. The transition gion

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