Well, there's already a clear volume difference between Cannons and Heavy Cannons but my guess right now is what you're hearing are Heavy Plasma Cannons.
They've got a very cool and deep sound effect.
And they're green.
For PvE (shooting the computer-generated enemies, etc), it doesn't usually matter what energy type you're using. About the least useful would probably be polaron, as the enemies are already so weak that an energy-draining proc won't make much difference. Same for phaser. . .disabling subsystems doesn't make much difference when the NPC ships are relatively easy to shred. Everything else is quite usable, just pick the one you like the look of and stick with it
For PvP, it's a different matter. In high-level PvP, it's usually recommended that you stay away from plasma beams. That's because almost everyone in high-level PvP is running anti-borg shields that reduce plasma damage by 20%. The other types are useful depending on your build and your focus. Anti-proton is especially useful for spike damage, due to the critical-damage bonus it gains. Polarons are nice in conjunction with an energy-draining build (siphons, Tyken's rift, etc). Disruptor's a good standby with it's damage resistance debuff, phaser is useful for catching players offguard with a subsystem disable, tetryon's useful for shield-stripping builds. . .
In the end, all the weapons have the same damage output per level. The only thing that changes is the graphics/sounds and (more importantly) the 'proc', or random secondary effect.
If your looking for loud cannons, there are four types that stand out. The first is the quad cannons you can get from the cstore. The second is antiproton very loud. The third is plasma cannons. Lastly you can polaron cannons which are decently loud.