Looking at Canadian law its worded similar to Texas law:
"Under Section 547.604 of the Texas Transportation Code, all motor vehicles must be equipped with a muffler, in good working order that prevents excessive or unusual noise. Further, the exhaust mufflers may not be bypassed.
Excessive and Unusual
Since Texas lacks specific decibel guidance, "excessive and unusual" is the applicable standard. In Aguilar v. State of Texas, a Texas appellate court reviewed a constitutional challenge claiming that the language was vague, and thus unenforceable since Section 547.604 does not specify a decibel level."
The argument didn't hold up in court. It's kind of odd you would get pulled over and cited for this. It's not like you were racing or doing something you were not suppose to be doing. Just make sure there are no local city ordinances for noise coming from vehicles. They may try to re file the charge. It's odd he wrote the ticket for no muffler unless excessive and unusual noise is under it.
So yeah you might get fined for that. I can't tell you how many muscle cars I see on the road that have modified exhausts and never get messed with. you happen to be in that 1%