Mazda 3 new brakes making a howling noise

Sept.3,2011 my mechanic change the front brake. And after installing the new brake. I am hearing like a dog howling noise specially in the morning
it's really terrible.I called my mechanic and he said it's normaI noise and it will go away. But it's been more than 1 month now I am still hearing these kind of noise. So I brought back my car to the mechanic Oc.3,2011 after 1 month observation and he said it's normal noise because the brake pad is new.I am worried my car is Mazda 3 2007 model.
Your advice is greatly appreciated.

Thank You