For SPL (Sound Pressure Level) measurements we would recommend digital microphone such as IMP34DT05, it is more simpler to implement with this vs analog microphone.
SPL level measurement reference code is available in FP-AUD-SMARTMIC1, this could be run on Nucleo development platform.
SPL library is part of other ST audio demonstrations, but it could be extracted as standalone feature from the source code, see below user manual and Chapter 4.5.5 for “dBNoise�?
Getting started with STM32Cube function pack for MEMS microphones acquisition, advanced audio processing and audio output - User manual
