External sounds audible in cockpit with engine running?

That's also my impression. And I was just sitting in a lousy Cessna ...

I dunno however if one could hear one's own machine gun firing as the Cessna had none installed

That's why I added the option gun sounds.

If you want to know if a fighter pilot could have heared a pilot behind him ask a veteran. Oh wait this was done many times. Not one of all accounts that I have read ever mentioned that they could hear other planes with their own engine running. In contrary they all concorde in that they could not hear it.

I however concede that the first option is badly phrased. Blame it on me not being perfect in English.

[ElAurens]

I've flown in a B-25 both in front (flight engineer's position) during run up, and in one of the waist gunner positions in flight.

Absolutely the loudest thing I have ever done.

If you were not on the intercom headset and wanted to talk to someone you had to SCREAM directly into their uncovered ear to be understood above the din.

I'm sure you could hear the sounds of the guns if you were the operator, but if you were the pilot and the waist or tail gunner opened up you would feel it (possibly) but not hear it. Even when we were taxiing out to the active, nearby civilian light aircraft could not be heard. Standing outside of a warbird is in no way comparable to being inside one. By comparison, the cockpit of a Cessna 172 is as quiet as a Rolls Royce Silver Cloud.