Audio mode an byte by byte are activated
Can't be, AFAIK.
Byte-to-Byte is only available in a Regular mode search.
Though, Audio mode, Match exact audio data, is available.
In that mode, AFAIK, DC runs a hash algorithm on the audio
data to find exact duplicates of the
audio data.
As a hash algorithm is being used, the hashes have to be computed.
(They may also be saved, base on the setting in, Settings | General | Use caching for calculated hashes.)
There are different hash methods (available via ffmpeg) that can be used, & not that I particularly understand them "enough", but on my end, for my purposes, I use (in a batch file that I came up with) a
stream copy method (rather then streamhash or framehash) because it's quicker & is sufficient - for me.