Fading in is the process of smoothly ramping up a signal's gain over a set period. In audio electronics, this prevents abrupt transients or popping noises when a channel is unmuted or a track begins. It is typically implemented using a voltage-controlled amplifier or a digital multiplier algorithm that scales the signal envelope.
Heard on the job
Program the DSP to fade in the microphone channel over 500 milliseconds to avoid a pop on the PA system.