This might be a forensics question, the answer to which is is the ENF signal (Electrical Network Frequency) which is used in forensics to locate certain associated acoustic and electrical signals in time for forensic purposes
ENF is a technique commonly used in audio forensics. It requires analysts to have recorded ENF signals over a long period of time.
PCM samples in a wav file are coded in 2's complement.
For a N bits sample size, it means that the maximum positive sample value is 2^(N-1) - 1 and the minimum negative value is -2^(N-1).
For N = 24, it leads to a maximum positive value of 2^23 - 1.
The maximum positive value of a sample composed of 8 lower bits set to 1 is 2^8 - 1.
So the dB FS value of ...