Emphasis
In FM transmission, emphasis is the intentional alteration of the amplitude-vs.-frequency characteristics of the signal to reduce adverse effects of noise in a communication system.
The high-frequency signal components are emphasized to produce a more equal modulation index for the transmitted frequency spectrum, and therefore a better signal-to-noise ratio for the entire frequency range.
The whole system of preemphasis and deemphasis is called emphasis.
The frequency curve is decided by especial time constants. The cutoff frequency can be calculated from that.
Emphasis is commonly used in audio digital recording, record cutting and in FM radio transmission.
See also Federal Standard 1037C and MIL-STD-188.
See also: Emphasis (typography).