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[Deesse23]

dB is a logarithmic scale,  105dB sound is 316 times more energetic than 80dB sound.   Adding 80.000 dB sound on top of 105.000dB sound yields 105.014dB sound, which rounds back down to 105db.   logarithmically the power in 80db sound is just too puny next to that in 105dB sound to register significantly on top of 105 dB.

Which is what I said earlier. At least I think that’s what I said - that you can’t simply add decibels. xdB + xdB doesn’t equal 2xdB.

Boru

You cant add dbs direclty, but the values add, and depending on the result your resulting db values ads numerically less.
dbs arent numbers but factors. You dont add factors. You convert to numbers and then go back to total factor.

Heres a good source if you want to understand the topic

http://www.sengpielaudio.com/calculator-db.htm