How I read a signal with sound() In Matlab

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hi

I have two signals first is input signal and others is noise signal I mixed two signals and got a signal, now I want play this signal with sound() function and I need frequency of it to play, how can I get the frequency of last signal that is a mixed signal?

as more information my code is like below:

[mainsigal, fs]=wavread('mainsignal.wav');
[noisesignal, fs1]=wavread('noisesignal.wav');%traffic signal
s=mainsignal(:,1);
n=noisesignal(:,1);
l_s=length(s);
for I=1:l_s
h(I)=s(I)+n(I);
end
sound(h,?????);
now I need compute fs for h signal.

thanks

Posted 22-Jan-15 5:40am

Sa.Mo

Updated 23-Jan-15 4:59am

v3

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CPallini · Accepted Answer · 2015-01-22T05:57:00

Solution 1

Quote:
how can I get the frequency of last signal that is a mixed signal?

You just need the sampling frequency of the original signal.

Posted 22-Jan-15 5:57am

CPallini

Comments

Sergey Alexandrovich Kryukov 22-Jan-15 12:11pm

Why sampling? Why original? Both signals equally contribute. The problem is not about sampling frequency at all.
Please see my answer.
—SA

CPallini 22-Jan-15 12:29pm

Because the OP has a signal of known frequency?
If you mix a sampled signal with white noise then you already know the 'sampling frequency' (that is the parameter requested by the sound function).
That has almost nothing to do with signal frequency (and hence with spectral analysis).

Sergey Alexandrovich Kryukov 22-Jan-15 12:48pm

Right, but the sampling frequency is not the only frequency involved. From the context of the question, it is even pretty much irrelevant. If you generate 440Hz la as a musical tone, the frequency of interest is that 440Hz, not much higher sampling.
—SA

CPallini 22-Jan-15 12:57pm

Well, if you want to play the signal using the sound function (like the OP asked), you have to provide the sampling frequency.

Sergey Alexandrovich Kryukov 22-Jan-15 14:10pm

So what? Consider this problem is already solved and address to the real problem. I already told you that I answered.
—SA

CPallini 22-Jan-15 15:04pm

I disagree. The OP as asked for the argument of sound, he/she doesn't need to perform a spectral analysis.

Sergey Alexandrovich Kryukov 22-Jan-15 15:12pm

We don't know what she/he really wants. I just say there is no one frequency. That's all. If there was one, there would not be a point to mix two signals. If they are mixed, some result of mixing should be played. We don't know the OP's criteria. The spectral analysis is needed to get at least some information. But maybe not. It depends on what's on input. If, say we knew that two input were two different sine functions, there would be no need for FFT. We just don't know what's on input.

Nobody says that there is no a sampling frequency, I just say this matter is trivial, not a part of this problem. The signal is audio, and sampling frequency is much higher, beyond the audible range, so this matter is pretty much irrelevant.

—SA

CPallini 22-Jan-15 15:34pm

Interesting as it might be, in my opinion, spectral analysis is simply useless in this case.

Sergey Alexandrovich Kryukov 22-Jan-15 15:36pm

You never explained why. You did not make any clear assumptions on what is that question about. Interesting? Pretty boring so far, I would say. :-)

Actually, I already admitted that FFT may not be need. My motivation is: this is about the "maximum of what could be involved". What is needed... as I can see, even OP has no idea. It would be correct to say: the problem, as formulated, has no solution, because it is undetermined. I'll edit it.

—SA

CPallini 22-Jan-15 15:40pm

Yes, it is boring, I agree.
I try to put myself in the OP scenario. If I have to play the signal via the sound function then I need to provide the sampling frequency, that's all.

Sergey Alexandrovich Kryukov 22-Jan-15 15:42pm

To play the signal, it's enough to play the sum of the two, as WAV. But OP wants to play on frequency. Strictly speaking, playing some one frequency had nothing to do with these two signals or its mixture, period. It could be anything.
—SA

CPallini 22-Jan-15 15:58pm

"To play the signal, it's enough to play the sum of the two, as WAV"
OK, I guess you eventually put the focus on the right button. This is what the OP is asking: "I have a sum of two signals, how can I play it with the sound function? It requires the sampling frequency as parameter and I have no idea...". Probably he/she has the signal (samples, hehe) inside an array. Sometimes questions are really naive.

Sergey Alexandrovich Kryukov 22-Jan-15 16:01pm

This mention of the "frequency" is clearly misleading. But the inquirer mislead herself/himself, that's the only reason to mention frequencies and, unavoidably, Fourier, not for "solving" the problem which does not really exist...
—SA

Sergey Alexandrovich Kryukov 22-Jan-15 15:55pm

So, I added [EDIT] to my answer to explain it all.
Yes, all those FFT references are probably redundant, but it may help to lead to understanding. There is no a solution, because there is no a valid problem.
—SA

Albert Holguin 22-Jan-15 15:46pm

+5, if you're combining two signals and all you're trying to do is play the combined signal, then all you need is the sample rate (or sampling frequency). I'd hope both signals were sampled using the same sample rate, otherwise you'd get some odd spectral anomalies that aren't really caused by the mixing of the original signals.

Sergey Alexandrovich Kryukov 22-Jan-15 15:56pm

[My mistake — SA]

Albert Holguin 22-Jan-15 16:14pm

No worries... I'm a communications engineer. ;)

CPallini 22-Jan-15 16:05pm

Thank you.

Sergey Alexandrovich Kryukov 22-Jan-15 16:12pm

Oh, I just found that OP actually looks for the parameter of the MATLAB function which actually expects sampling frequency, and the signal is known.
Sorry for not paying attention.
5ed.
—SA

CPallini 22-Jan-15 16:25pm

Thank you very much, Sergey.

Albert Holguin 22-Jan-15 16:21pm

...and if you're combining two signals of two different sample rates, they must be resampled to the same rate first before combining...

Sa.Mo 22-Jan-15 16:31pm

I am confused please tell me some example code

CPallini 22-Jan-15 16:38pm

You don't need sample code. How do you represent the sum of the two signals? Is it inside an array? Is it an analytic function, e.g. s(t) ?

[no name] 22-Jan-15 19:18pm

At this point it may be better if you improve your question and explain clearly how you got your 2 input signals and maybe show your code. The rest is easy.