Try a different make/style prop. You don't say what brand/style prop you are presently using, but I have found that a Master Airscrew prop (the black one ) is noisier and not as efficient as an APC. When I switched from a MAS to an APC my db level dropped several points since the APC doesn't flex as much and the style doesn't "beat up" the air as much.

If you do not have a baffle in the muffler, try an OS muffler with the baffle in place. While it will reduce your power a little, it will quiet the motor. Another thing you can try is an exhaust deflector. This will also reduce your power a little, but will also help to reduce the noise.

I would try the APC prop first, then go from there.

FWIW - Seal the backplate and the carb o-ring with some silicone. Tower 46 engines are well known for their air leaks so that the engine will not shut off right away with the transmitter (takes ABOUT 15 - 45 seconds for the engine to die ).

Hope this helps.