This is more of an engineering problem, not usually considered by music listeners unless designing a sound studio. Well, at least it's not, not an engineering problem. Since AI is now on the scene, I got this answer by asking Bard. https://g.co/bard/share/517852dd66b8
The total sound level is approximately 60.043 decibels
AI often sounds convincing while providing an inaccurate answer. I got this answer by asking Chat GPT. It arrived at the same formula as Bard
dBtotal = 10log(10^(60/10) + 10^(40/10))
but came out with a different end result to the calculation.
https://chat.openai.com/share/e1c844df-ac8d-4b74-a18d-b071523d8151