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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).
