1993 Buick Riviera Owner's Manual - Page 127
1993 Buick Riviera Manual
Page 127 highlights
A CAUTION: Hearing damage from loudnoise is almost undetectable until it is too late. Your hearing can adapt to higher volumes of sound. Sound that seems normal can be loud and harmful to your hearing. Take precautions by adjusting the volume control on your radio to a safesound level before your hearing adapts to it. To help avoid hearing loss or damage: Adjust the volume control to the lowest setting. Increase volume slowly until you hear comfortably and clearly.