a process of increasing the amplitude of certain frequencies relative to others in a signal in order to help them override noise, complemented by deemphasis before final reproduction of the signal being received. Found on https://www.infoplease.com/dictionary/preemphasis
1) Predistortion 2) Preequalization 
a process of increasing the amplitude of certain frequencies relative to others in a signal in order to help them override noise, complemented by deemphasis before final reproduction of the signal being received.