{{Harflertydig}}
[[Fil:RIAA-EQ-Curve rec play.svg|thumb|RIAA-forbetoningskurven (blå), som anvendes ved optagelse på vinylplader, reducerer lave frekvenser og øger høje frekvenser.<br>RIAA-efterbetoningskurve (rød), som anvendes ved afspilning, udfører den omvendte funktion, øger lave frekvenser og reducerer høje frekvenser (og højfrekvent (rille)støj).]]
Inden for [[signalbehandling]] er '''forbetoning'''<ref>[https://denstoredanske.lex.dk/forbetoning denstoredanske.lex.dk: forbetoning], [https://web.archive.org/web/20230618105307/https://denstoredanske.lex.dk/forbetoning backup]</ref> en teknik til at beskytte mod forventet [[støj]]. Ideen er at forstærke (og dermed forvrænge) det [[frekvensområde]], der er mest modtageligt for støj på forhånd, så der efter en støjende proces ([[Transmissionslinje|transmission over kabel]], [[båndoptagelse]], [[radiokommunikation]]...) kan bibeholdes mere information fra det frekvensområde. Fjernelse af forvrængning forårsaget af forbetoning kaldes '''efterbetoning''', hvilket får outputtet til at gengive det originale input nøjagtigt.<ref>Betoningseksempel; vinylplader: [https://www.stereophile.com/features/cut_and_thrust_riaa_lp_equalization/index.html Apr 2, 2009, stereophile.com: Cut and Thrust: RIAA LP Equalization] Citat: "...To obviate this and produce the constant-amplitude cut we desire, electronic equalization (called preemphasis) must be applied to the signal fed to the cutter. Ideally, this preemphasis needs to double the signal voltage for every doubling of frequency, equivalent to a 6dB/octave rise throughout the audible frequency range. This is illustrated as the red line in fig.2 alongside the actual RIAA preemphasis curve (blue), which doesn't deliver an exact constant-amplitude cut but a fair approximation of it....to restore a flat frequency response, replay equalization (deemphasis) that is the inverse of the record equalization must be applied. This is done in the disc input stages of the replay system's preamplifier (footnote 1). The RIAA pre- and deemphasis curves are defined by three time constants (T), each of which is related to a corner frequency (f) in the amplitude response by the equation:...These time constants (3180, 318, and 75 microseconds) and their respective corner frequencies (50.05, 500.5, and 2,122Hz) are depicted in the red trace of fig.3, which shows the straight-line approximation of the RIAA deemphasis (ie, replay) curve, alongside the actual curve (blue). Note that the latter is a mirror image of the preemphasis curve in fig.2, so that the two are exactly complementary: applying the deemphasis on replay cancels the effect of the preemphasis applied during cutting, to leave a flat response overall (footnote 2)..."</ref><ref>Betoningseksempel; FM-radio: [https://www.daenotes.com/electronics/communication-system/pre-emphasis-and-de-emphasis daenotes.com: Pre-Emphasis And De-Emphasis] Citat: "...Pre-emphasis refers to boosting the relative amplitudes of the modulating voltage for higher audio frequencies from 2 to approximately 15 KHz...De-emphasis means attenuating those frequencies by the amount by which they are boosted...", [https://web.archive.org/web/20230204025816/https://www.daenotes.com/electronics/communication-system/pre-emphasis-and-de-emphasis backup]</ref><ref>Betoningseksempel; FM-radio: [https://www.rfwireless-world.com/Terminology/Pre-emphasis-vs-De-emphasis.html rfwireless-world.com: Pre-emphasis vs De-emphasis] Citat: "...As we know noise usually will have higher amplitude and higher frequency components. This high frequency noise will lead to frequency distortion when its amplitude is higher than the components present in the modulating signal. To overcome this situation most of the FM circuits use techniques known as Pre-emphasis at the transmitter and De-emphasis at the receiver...The Pre-emphasis helps amplify high frequency signal components such that they will have magnitude higher than noise components. This lead to improvement in the Signal to Noise Ratio i.e. SNR...The De-emphasis does exactly reverse of the Pre-emphasis counterpart. It is used at the receiver part...", [https://web.archive.org/web/20230618113334/https://www.rfwireless-world.com/Terminology/Pre-emphasis-vs-De-emphasis.html backup]</ref> Efterbetoning bliver også kaldt '''korrektion''' eller '''udligning'''.
Samfund Datalogi Biblioteks-_og_informationsvidenskab Kultur Teknologi Matematik