Toyota: engin noise, accelerator pedal, low pitch

Question
I have a corolla 96 1.8 manual about 100k miles. The car runs very well both on highway and on city road but recently I noticed a noise coming from engine. The noise is noticeable as soon as I started car. It changes to high pitch noise when I push the accelerator pedal and back to low pitch noise when I release the pedal. The noise is not a metal quality and there is no vibration comes with it. I have this car for about 8 year. This is a new noise.
Recently, I have the dealer changed cooling fan control unit and the coolant as well. The timing belt has been changed also recently. The noise came after these repairs.
The car is regularly maintained. Last oil change was in May. There is no oil leakage.

Thank you very much

Answer
Hello,

it seems that something went wrong during last repairs! Maybe something involved with the timing belt...
MAybe it's only the TB whick touches some plastic or metal part, but in any case have it checked, it's mechanic's fault!

Regards,
Jack