How Does Speed Sensitive Volume Control Work?by Robert Moore
Speed sensitive volume control --SVC for short -- works by adjusting the volume of your radio in relation to the speed of the vehicle. As you accelerate the radio will gradually increase in volume, or decrease as you slow down, to keep the ratio of cabin noise-to-radio volume the same. This system is normally only active at speeds above 35 mph, but this may be different depending on the manufacturer of your vehicle or audio system.
How the Radio Knows
On stock radio systems, the volume is automatically controlled based on the speed of the vehicle and the ambient noise inside the cabin. If you have an aftermarket radio that is equipped SVC control, the volume is based solely on cabin noise. Stock radios often use the same microphone that is used for hands-free calling, while aftermarket radios have specially installed microphones to measure the noise in the cabin. Depending on the manufacturer of your vehicle or radio, you may have the option to disable this feature, or choose between different levels of sensitivity. Review your vehicle or radio's owner's manual to see what options are available to you.