Low RPM Noise after Timing Belt Replacement

Thanks for your response! I did take it back to them, but the mechanic didn't hear the noise I was talking about. The noise does disappear above 2300-2500 RPM, but below that it's pretty noticeable to me since I've been driving the car for 11 years. I was told that the tension was automatically set by the tensioners and therefore the belt shouldn't be too loose or tight. Do you have any suggestions on how to proceed when the mechanic isn't hearing what I'm hearing?

Certain brand of timing belt will cause that, especially GATES brand. Are you changing the stock OEM brand ?