You'll find this in several threads, with only a couple of the fixs working. Several explanations but no set in stone word on what it is causing it. My 2000 Z71 Silverado did the same thing. So far, I just turn the radio up & ignore it. GM hasn't said outright that it's a defect so I'm living with it for now untill the rest of us SSR owners find out exactly what it is.
One of the mysteries of the SSR.
One of the mysteries of the SSR.