Not sure if they still make them, but they used to have a baffle for straight pipes that looked like a washer with a knob on one side. Took a single 3/16" or 1/4" hole in the side of each pipe to install them. A 1/4 turn on each knob would close them to restrict sound, or open them to make them straight pipes.
We used to make them up ourselves also to save money. Weld a 1/4" all thread rod to the side of a 1.5" washer, then drill the exhaust and feed the threaded rod through the pipe. Put a small spring on the outside, then a nut, and lock it against a wingnut. You have a cheap, easy baffle, that can be turned to either direction to quiet it down, or leave it noisy.