Note that there is no calibration of audio hardware, so the level of usefulness of any such software would be strictly limited.

Will Oscilloscope fulfill your need?

There is “Oscilloscope” which can show frequencies and their intensity

See https://f-droid.org/packages/org.billthefarmer.scope/

OpeNoise is one… it will need calibration but if you weren’t concerned about actual dB readings you could use it uncalibrated