I tried a similar experiment with the ultrasonic leak detector I am selling on another thread.
The leak detector has a noise generator option, which I bought.
I made a 4" pvc pipe capsule with an air fitting adapter on one end and piped it into the system, and you could hear it thru the piping.
Granted not as loud as when I put it in the bus and was under it looking for any potential critter holes, or trying to find the air whistle noise on the entry door,"which it did find".
But it did work for all those jobs.
As well as a stand alone leak detector.
I dont know how sensitive the ones some of you guys are using are, but this one, for example, if you just slightly, just barely, rub you finger tips together it sounds like someone is rubbing to bricks together on top of your head.
It found leaks I could not find with gallons soapy water.
I was going to try my freon sniffer but this did it so I didnt bother, excellent idea though.