Reducing a signal level by fixed equalization (usually high frequency roll-off). An example would be Dolby noise reduction.
The modulation in a radio system where the modulation level (deviation) falls as the frequency rises. Any circuit or signal where the amplitude falls as the frequency rises.
A reduction in the amplitude of the higher frequency portions of a frequency modulated signal (e.g. analogue television) and its accompanying noise after transmission via a radio link. De-emphasis is used in conjunction with a complementary Pre-Emphasis device in the transmitter so that their combined effect on the signal is neutral. The pre-/de-emphasis process improves the signal-to-noise ratio for high frequency signal components and thus the overall quality of the received signal. See also Pre-Emphasis.