Noisy Acceleration after Timing Belt Change

I just had my timing belt and balance shaft belt replaced at a mechanic shop. After I picked up the car (01 Honda Accord) there is a very noticeable low hum when accelerating. The acceleration is sluggish. I requested to recheck the alignments of the marks and the belts? tension and they seems ok. What is going wrong?

Good question. The engine should sound and run the same after a timing belt installation as it did before.

Did the mechanic replace anything other than the belts, such as the water pump or tensioner pulley?