Dolby Laboratories 430 - Manual (Page 6)

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INTRODUCTION
The Model 430 Series is a playback-only noise reduction system intended primarily to reduce unwanted
ambient noise from location recordings. Typically, this noise is generated by broadband sources such as
generators, wind, or traffic.
The Model 430 Series is a second-generation design, following from the Cat. No. 43 unit—a successful
background noise suppressor in widespread use in post-production facilities throughout the world. The
Model 430 unit offers several benefits over the earlier design, including improved ease of operation, and a
reduced risk of side effects.
The earlier design was based on Dolby A-type noise reduction techniques, and incorporated user control of
each of its four fixed bands to accomplish playback noise reduction. The Model 430 design is based on
Dolby spectral recording techniques, with a multiple combination of low- and high-frequency fixed and
sliding bands. Basic user controls have been reduced to two, controlling the amount of playback noise
reduction above and below the dominant signal of interest, typically above and below mid-frequency dialog
components. The use of Dolby SR fixed and sliding bands in combination results in much more stable
signal handling with a significantly reduced chance of audible background signal pumping. Nevertheless,
the user is cautioned that, as with all non-complementary playback-only noise reduction devices, excessive
use and certain signal combinations can lead to audible side-effects.
The Model 430 Series is not intended for suppression of spot-tone signals, such as camera noise or power
line hum interference. Noise sources such as this may well be better treated with a dip filter.
In typical applications, the Model 430 Series unit is placed in the signal path of a sound mixing console
where nominal line levels are present. It is intended to operate at a level around +4 dBr (Ref: 0.775 Vrms).
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