Have someone record you. You can check for a bad release (pluck, finger drag, etc.), loss of shoulder tension (forward creep, shortened draw length, etc).
It would also let you check to see if the noise is just a matter of perception.
I always think I have a soft “thump” on the shot....have had my wife and kids try to listen ...they heard nothing...didn’t even know when I shot if they had eyes closed. Long story short, I didn’t believe them, so I had them video tape it. Played it back and could hear nothing. I had about gone crazy trying to quite....what was already silent.