| 释义 |
pre-ˈemphasis Sound Recording and Broadcasting.
[pre- A. 2.]
A systematic distortion of a signal prior to transmission or recording, involving an increase in the relative strength of certain frequencies in anticipation of a corresponding decrease during reception or playback.
1940RCA Rev. Jan. 359 The use of pre-emphasis circuit [sic] at the transmitter and a de-emphasis circuit at the receiver produces an overall gain in signal-noise ratio. 1942, etc. [see de-emphasis]. 1959K. Henney Radio Engin. Handbk. (ed. 5) xxi. 35 Below 100 cycles the characteristic of the [disk] recorder system is made constant-velocity by electric means. This tends to give preemphasis to the low frequencies... Above 500 cps a preemphasis above a constant velocity is given to the high frequencies, especially over the noise frequency range. The necessary characteristic for reproduction is the inverse of this curve. 1977Gramophone Mar. 1476/3 The most important of these is the ‘breathing’ or ‘pumping’ effect as residual noise is heard rising and falling in level as the expander alters system gain in response to sudden changes in signal level... High frequency pre-emphasis, followed by mirror-image de-emphasis, reduces the effects of breathing.
So pre-ˈemphasize v. trans., to subject to pre-emphasis.
1968Cook & Liff Frequency Modulation Receivers xiv. 490 Both the left (L) and right (R) channels are fed to 75-µ sec high-pass filters, where they are preemphasized. 1974M. Mandl Mod. Television Syst. ii. 29 The higher audio-frequency range at the transmitter is preemphasized. 1977Gramophone Mar. 1476/1 A dodge of this kind is universally employed in VHF/FM broadcasting, where high frequencies are boosted (pre-emphasized) at the transmitter and attenuated (de-emphasized) at the receiver. |