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I've conducted a measurement of underwater noise in a laboratory experiment. Therefore i am using a sweep signal.

Sometimes -I guess when the signal is much more louder- I get this fascinating repeating and kind of symmetric pattern when I analyse the signal. Can someone name the physical phenomena involved which are causing this?

The picture below shows the response without Pattern:

Signal without repeating Pattern

Response with repeating Pattern:

Signal with repeating Pattern

The only difference I can find is that the recorded response is much louder. I am still clueless and fascinated which physical phenomena might be the cause of the

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My first guess is that this is clipping or some other form of non-linear distortion. If you clip a sine wave you end up with mostly odd harmonics. You have some even ones in here too, but they are a lot weaker.

So chances are: something in your signal chain is overdrive: could be the DAC, the power amp, the transducer itself (quite likely), the microphone, the pre-amp, the ADC, etc.

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  • $\begingroup$ Thank you. Can you think of any other reason this occurs? Yes it is a sine sweep roughly starting at 10 Hz up to 700 Hz. Can you please try to explain how clipping exactly results in this pattern? $\endgroup$
    – hoaratius
    Sep 23, 2023 at 16:40
  • $\begingroup$ @hoaratius, this is well documented in the Exponential Sine Sweep (ESS) method. You can find some information about it in the following links: dsp.stackexchange.com/a/86924/40198, dsp.stackexchange.com/a/87031/40198, dsp.stackexchange.com/a/41700/40198. You can also search for information about the method online. A Google search for the method will give enough information (the researcher who introduced it is Angelo Farina, in case this helps). $\endgroup$
    – ZaellixA
    Sep 23, 2023 at 17:00
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    $\begingroup$ Okay. Thank you both for your help. Appreciate it a lot. And thank you both for taking time and answering my question @ZaellixA $\endgroup$
    – hoaratius
    Sep 23, 2023 at 18:14

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