# Interpreting Auto correlation results

I used xcorr function in Matlab to compute the autocorrelation of my signal. I obtained a graph, which is shown below. How to interpret this? I read that autocorrelation helps in finding the patterns in the data. And i have went through some of the properties of the auto-correlation.

But i am finding difficulty in obtaining information regarding how my input data is correlated with itself. Do i need to compute any other things in order to get this information? How to understand the autocorrelation graph?

• Can you provide a zoomed-in plot of the two large peaks, around t=1.4? – MBaz Mar 5 at 2:15
• Yes. I attached it with the question. Please have a look. – Ramakrishna Mar 5 at 2:44
• What kind of signal are you analyzing? What "patterns" are you looking for? The autocorrelation basically indicates how similar a signal is to a shifted version of itself... – applesoup Mar 5 at 11:02
• I am trying to analyze the noise coming from the table fan. I observed that it is almost a periodic signal. Above one is autocorrelation result of that. I wanted to know what does autocorrelation indicates in case of this signal. – Ramakrishna Mar 5 at 15:08