or pre-em·pha·sis

noun Electronics.
  1. 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.

Origin of preemphasis

First recorded in 1940–45; pre- + emphasis Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019