This is a nice YouTube video that shows the effects of a suppressor:
It’s a Glock 19 with a suppressor on it. 10 rounds are fired. The first 5 are 115 grain bullets and the second 5 are 147 grain bullets. The reason that matters is 115 grain 9mm rounds tend to go maybe 1200 feet per second, which is faster than the speed of sound; whereas 147 grain tend to go slower than the speed of sound (900-1000 fps). While a suppressor can do something about the escaping gases, it can’t do anything about bullets breaking the sound barrier, going supersonic, and creating the sonic boom (the crack).
Suppressors are wonderful things. Helps to save your ears, helps to keep your neighbors happy.