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I work in the field of phonetics and often need to record human speech for acoustic analysis. I have two questions that I couldn't find answers:

If I record in stereo channels, I need to convert to mono later on to proceed with annotation. So in principle mono signal is good enough. Are there reasons that stereo sound should be used (e.g. the signal would be better?)

Also, we were warned that the gain level should be kept small so that the recording level shouldn't exceed the maximum, which leads to signal cuttoff. However, I was also criticised when the recording file shows too low an amplitude (it's still very clear though), for that leads to a low SNR. How do people choose an appropriate gain level?

Cocoa
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  • This isn’t an appropriate topic for SO. I’d recommend the DSP stack exchange. You say _”we were warned…”_ so my recommendation is to pose this question to whomever gave you that warning. – fdcpp Jun 21 '22 at 11:44

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As the act of recording is involved, the Sound Design forum might be your best bet.

I can't think anything that might be gained, in terms of frequency analysis, by having a stereo signal. Stereo is more about locating the source of a sound in 3D space. Does the source of sound emit different frequency profiles in different directions? Does the environment filter the sound differently over the course of the two paths to the stereo inputs? If the the answer is "not significantly" then mono should be fine.

Choosing an appropriate gain level is mostly a matter of knowing your equipment. Ideally, your recording setup will provide feedback (usually a visual meter of some sort) that shows the signal strength. The "best" would be (theoretically) the loudest level that does not distort. So you have to know at what level distortion happens on all the elements of the recording chain.

There can be some fudging on this, given that the loudest peak on a recorded segment may be an outlier.

Phil Freihofner
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