https://www.oneida-air.com/inventory...-4D6E6324DF13}
I saw these at IWF and while hard to judge in the high ambient noise of IWF I am pretty sure it makes a solid difference. They say 6-7dB @ 10 feet. This means a reduction of sound energy to 1/4 (or slightly more) of what it would be without the muffler, note human perception of sound doesn't quite work that way, we here a 10dB reduction/increase as halving or doubling the "volume".
The pictures on the site (not link friendly) shows a simple cylinder lined with "egg crate" acoustical foam. For the price (170-200 depending on the size) someone could build something using Sonotube for much cheaper. There are also sound absorbing materials much more effective than simple egg crate that could produce an even larger drop. But it is a simple, seemingly effective, solution for those not interested in playing with tubes and getting them to seal.