Belt noises

I recently replaced the serpentine belt and alternator belt on my Saab 9-5. An idler pulley was also replaced at the same time. The new belt chirps loudly at startup, then gradually disappears as the engine warms to normal operating temp. It seems to be lessening in loudness and duration, as I use it. But, it annoys me and I am worried about whether everything was replaced properly. What’s the cause and the fix?

Take it back and let them correct it. I’m sure their work is guaranteed.