1996 Avalon XLS Engine Noise

[Sarma]

My 1996 Avalon XLS (150,000 miles) engine just in the past couple of days has started to make noise. It begins the moment I start the engine. The sound is loud and is very similar to a turbo-prop plane. When I accelerate, the whining / noise appears to increase. When I reach a cruising speed - I do not hear the noise and it is probably because the road noise takes over. Few days ago I had an oil change done and had all the fluids checked. The car passed a 27 point inspection from the dealer. Now this sound has started. Could it be something that the dealer did to teh car during oil change? Any clues on where the noise is coming from ? Any guidance will be greatly appreciated.