- Preemphasis
In processing electronic audio signals preemphasis refers to a system process designed to increase, within a band of frequencies, the magnitude of some (usually higher) frequencies with respect to the magnitude of other (usually lower) frequencies in order to improve the overall
signal-to-noise ratio by minimizing the adverse effects of such phenomena asattenuation distortion or saturation of recording media in subsequent parts of the system. That is the mirror of thedeemphasis . The whole system is called emphasis.The frequency curve is decided by specialtime constant s. Thecutoff frequency can be calculated from that value.Preemphasis is commonly used in
telecommunication s,digital audio recording, record cutting, inFM broadcasting transmissions, and in displaying thespectrogram s of speech signals.An example of this is the
RIAA equalization curve on 33 rpm and 45 rpm vinyl records.In high speed digital transmission, pre-emphasis is used to improve signal quality at the output of a
data transmission . In transmitting signals at high data rates, the transmission medium may introduce distortions, so pre-emphasis is used to distort the transmitted signal to correct for this distortion. When done properly this produces a received signal which more closely resembles the original or desired signal, allowing the use of higher frequencies or producing fewer bit errors.See also
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Federal Standard 1037C andMIL-STD-188
*Preemphasis network External links
* [http://www.sengpielaudio.com/calculator-timeconstant.htm Preemphasis - Frequency response and equalization EQ - Conversion: time constant to cut-off frequency and vice versa]
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