Loud moaning noise under the hood when gas pedal is pushed down to go

When you push your gas pedal you are revving the engine, so anything that's attached to the engine that spins will spin faster - such as your belt pulleys, your alternator, and your power steering pump - especially the power steering pump. I'd check the power steering pump's fluid level, when it's low it can make a groaning noise. (does the noise occur when you turn, too?) If that's fine check all the belt pulleys, especially the idler pulley and the belt tensioner. Let us know what you find out.

A moaning noise could be the induction sound of air being sucked into the engine. If it is to loud maybe something in the air intake system has come loose.