2000 Pontiac Sunfire noise coming from altenator area

I just a 2000 sunfire gt,2.4 twin cam a month ago, I had the altenator and belt replaced and all four brakes replaced .After going to the car wash a week ago (I didn't wash the engine just the outside of the car) my car makes a whirling/squill noise coming from the altenator area. It only makes the noise travelling under 30km/h when i step on the gas and speed up to 50km/h the noise goes away. I'm not stepping on the brakes . I put belt dressing spray on the belt. Car runs fine . so far the only thing i can think of to get rid of the noise is just turn the stereo up