I was an infantryman once. Occasionally, we would be assigned to armor units. 
Tanks, at that time were M48 Patton. They used a V12 air cooled Continental gas engine.
The engine sound is but one small part of an M48 in action.
Fun fact about a Patton. I think they suck cool air for engine cooling from under the tank, They exhaust the hot air out the rear. If, by chance, the tank would run over an un-dispersed 50 lb. paper bag of CS powder, suck the powder through the engine, and blow it out the rear, any poor infantryman walking behind the tank would be treated to a facefull of CS powder.