This is a simple sound generator to produce jet engine aircraft sounds and it will run on any battery voltage between 3v and 40v.
The circuit will produce 4 sounds : low speed sound of aircraft, high speed sound of aircraft, missile and machine gun. They are activated by connecting pins 12, 13, 14 or 15 to ground respectively.
http://www.ef-uk.net recorder 2 sound files whilst testing the unit the first file is each of the four sounds in order and were recorded with a fixed 430k resistance between pins 10 and 11.
The second file is the low speed sound with manually changed resistor to increase then decrease the engine speed.