Sounds like a Cement Mixer
 

2009 4 cyl camry, 46K miles.
It's my 1st 4 cyl, I'm an old V8 guy. Like to hear the engine Purrrr at Idle.
This thing sounds like a Cement Mixer. All fluids at correct level and sound seems to come from internal engine. Ps, Air, Alt == no noise coming from them.. The question is..
Is this a normal sound???
Thanks..

Might check water pump. Follow the lower radiator hose to the engine. Water pump is located further toward the passengers side of engine and powered by the serpentine belt.

The engine uses a timing chain instead of belt, location behind front cover on passengers side of engine. The head has to cams and thus two chain driven pulleys.

Check serpentine idler pulley. Location, above crank pulley and on fireside side of PS pulley.

Check your pulleys also. I had a similar problem and that is what it was.