What is Emphasis? Emphasis is the process of boosting the Amplitude Vs Frequency characteristics of a signal to reduce the effects caused by noise while transmission or reception of message signal over the channel. The noise that may occurs include both single frequency interference and thermal noise. Noise is inherently greater in amplitude at higher modulating signal than at lower frequencies, because the signals with higher frequencies have low SNR (Signal to Noise Ratio). By emphasis, approximately a 12db of improvement in noise can be achieved in FM. Read More.....