2002 GMC Sonoma Owner's Manual - Page 188

AM-FM Stereo with Cassette Tape and Compact Disc Player with Radio Data System (RDS) and Automatic Tone Control (If Equipped) Playing the Radio PWR (Power): Press this knob to turn the system on and off. VOL (Volume): Turn this knob clockwise to increase volume. Turn it counterclockwise to decrease volume. AUTO VOL (Automatic Volume): With automatic volume, your audio system adjusts automatically to make up for road and wind noise as you drive. Set the volume at the desired level. Press this button to select LOW, MEDIUM or HIGH. AVOL will appear on the display. The volume level should always sound the same to you as you drive. Each higher volume setting allows for more volume compensation at faster vehicle speeds. Then as you drive, automatic volume increases the volume as necessary to overcome noise at any speed. NONE will appear on the display if the radio cannot determine the vehicle speed. If you don't want to use automatic volume, select OFF. 3-34