Measure of noise intensity

[Jens Noriʇzsɔɥ]

Get negative dB?
Calibrate.

How to calibrate?
Get positive dB from other soundmeter app.

Thanks, Roland, for pointing this out. That has fallen short in my reply.

For the sake of completeness I also add our “disclaimer”, see phyphox.org/wiki/index.php/Experiment:_Audio_Amplitude:
“Even a well calibrated experiment is still limited in its accuracy as the experiment does not take into account the base noise, the spectral dependency of the microphone, non-linear responses and directional dependencies. So, this experiment may be suitable for simple educational purposes, but for serious measurements you will either need a dedicated app for your device or, much better, professional equipment.”