No cross-correlation between same signal recorded using two different microphones I've recorded the same audio signal using two microphones located at the same approximate location. However, when checking the cross-correlation using MATLAB (using the xcorr function) it is negligible, even though the signals look approximately the same and sound the same. The signals were brought to MATLAB using the audioread function. This scenario was repeated using a different set of microphones, achieving the same results. 

Did anybody encounter this kind of problem in the past and has a solution?

EDIT:
First of all, thank you all for the help.
This is a scenario of two sources and two microphones in different locations in space. The signals clearly sound mixed (each signal contains both sources) and the microphones are synchronized and at the same sample rate of 44.1kHz.
The code:

[x1,Fs1]=audioread('channel_1.wav');
[x2,Fs2]=audioread('channel_2.wav');
figure; subplot(2,1,1); plot(x1);subplot(2,1,2);plot(x2);
[R_11,lags]=xcorr(x1,x1);
R_22=xcorr(x2,x2);
R_12=xcorr(x1,x2);
figure;plot(lags,R_11);hold on;plot(lags,R_22);plot(lags,R_12);


The correlations:



The signals:
This answer is now obsolete.

I still keep it, because future searchers might come here with similar problems. 

This is not the signal as it is now, but as it was before, when I answered:



I'll do a hypothesis: the autocorrelation peaks are due to periodicity in your signal. But if that's the case, they should be the same for $R_{11}$ and $R_{22}$.

My guess is that you're comparing two recordings of different sampling rate (for example, 44.1 vs 48 kHz). But xcorr only sees the vector of numbers and doesn't know about the sampling rate!