Loud Engine Noise, But Only in Cabin

[N. Flores]

02 Lancer ES Automatic 55,000 miles
Just bought. Was running very quiet. Everything checked out and all good. Now it sounds like I have a huge engine in a tiny car. Idles fine and quiet. No vibrations. Absolutely no noise when outside the car. Gets loud when I accelerate. All noise is in the front most part of the cabin. Not running hot. Idles and revs normal. No odd smells and no loss of performance.