There is something else could be done with an electronic sound, which is to delay it slightly after the visual cue so as to simulate the scale distance between the viewers and the ship.
Of course you'd need to vary that time with how far away it is.
If I had an aunt, she'd be giddy. And probably in need of a small glass of sherry.
I have a microchip here: an MPU 6050. It cost about £3 and is currently plugged into an Arduino for
secret research purposes*.
The chip is a self-contained, solid-state inertial measuring unit. If put in a boat and switched on at the lakeside, you could sail around literally all day and - by integrating the accelerations & rotations - calculate by dead reckoning exactly how far the vessel is from you.
The speed of sound at 1/72 scale is 4.7 metres per second. So, if the boat's 30 metres away, delay the sound by 6.3 seconds...
All do-able.
Andy
*secret research purposes? Prepare to be
at least a little impressed. I'm coding at the moment, early results look good, but the possibilities are quite extraordinary.