Benjamin Marauder 177 got louder

As the title says, my stock, two year old .177 Marauder LW suddenly is way louder than it was before. I always use the same H&N 8.65gr Field and Target pellets. My air pressure is usually between 2000 and 2400 which is the sweet spot for this gun and my 20-30 yard prey. When I first set this up, I was getting 850-950fps but have not tested again. Still, It does not sound like it is going supersonic. I compared it to another 177 Marauder (non-LW, wood stock) with the same pellets and that is noticeably quieter like I remember mine to be. What could be the problem?

Second question is what is a good add on Moderator for this platform? BTW, I have a DonnyFL Sumo on my .30 FX3 and Impulse Air Moderator stack on my .22 FX3. Both are excellent at keeping the noise down.

 
Agree on the breech seal . . .

I can't imagine that a moderator will do much for your Marauder, as they don't do much for my .22s running about 30 FPE - the guns are already very quiet. If you want yours quieter, the best thing do to is no cost - remove the front shroud mount and drill out the vent holes to a larger size. This will let more air into the back of the shroud and will absolutely make it quieter. The mount is plastic, so it is easy to drill, and it will be plenty strong with bigger holes, as long as you don't over do it.