General Sound Modules

[Capn Pete]

I don't know if that is what they're called, but am looking into getting one. These are the devices that simulate engine sound. I used to know what they're called and where to find them, but have forgotten.
Thanks,
Pete

 

[Admiral]

Try Model Sounds Inc. - The Ultimate in Radio Controlled Model Sound Systems or https://hobbyking.com/en_us/fixed-wing-aircraft-sound-module-hobbyking.html have some very simple ones which are cheaper.