The image shows the Spectrum mode of this app https://f-droid.org/en/packages/org.billthefarmer.scope/

Im hissing in this picture (peak around 7kHz) and there is a loud AC unit going which is all the low frequency humming on the left. It just uses your built in mic so thats going to be the biggest limitation in terms of precision, but it works very well even with that as you can see.

Try phyphox https://play.google.com/store/apps/details?id=de.rwth_aachen.phyphox