When I first started with my department in the early 90's, only the 2 newest fire engines were fully enclosed. What that means is that on most of the fire trucks, the officer and the driver were up front in the cab, and the firefighter(s) were sitting on the "jump seat" behind them. The jump seat was facing backwards and under an overhang of the cab, there were no doors, you just sat there "riding backwards and smelling diesel" as they say. We were separated from the guys in front by the back wall of the cab of the truck.
And it was loud for the firemen on the seat too. The motor of the truck was right beside us, there was wind noise, and road noise. We couldn't hear the radio, or the officer. Basically, you just got on sat down and then took orders from the officer after you got there.
Soon after I started, the department decided that an intercom system would be a good thing. (and boy were they right!) The city installed headphones with a microphone in every position of the trucks. Now, the officer could talk to the driver without yelling, and give the firefighters orders before we even got to the scene.
But, like a lot of things, it was a chance to play around too.
One day, on a routine trip to the store, an officer and driver in the front pretended that the intercom wasn't working in the back. They kept asking the fireman "can you hear me? Say something." The fireman would reply, but of course they pretended not to hear.
Now the fireman knew that the intercom was a new toy. And he also knew that several problems had actually occurred with the new system. He wasn't really surprised that it wasn't working right. So when the officer kept asking him if he could hear him, he started to reply things like "For the 100th time I can hear you. How did you get to be captain if you can't figure out by now what's happening?".
As the drive went on, since no one could hear him anyway (but he could hear himself in the earphones) he started playing.
"Redbird one to redbird leader, bombs away!"
"Breaker breaker one nine, come back good buddy"
"Mayday! Mayday! We're losing power"
"I'm givin her all she's got Captain, I'm tellin' ya she can't take anymore!"
Might have even sung a song or two.
Finally the officer and driver couldn't stand it and started laughing at the fireman.
That's when I realized they could hear everything I said.
I'll be glad when those old bastards retire. They tell that story every time they see me.