When the music is loud, the low background hiss level is not noticeable, but when the music is soft or in silence, most or all of what can be heard is the noise. The signal-to-noise ratio is simply how large the music signal is compared to the low level of tape noise with no signal. Noise and frequency response analysis of a Nakamichi 580M high-performance cassette deck with Dolby B-type noise reduction systemĭolby noise reduction is a form of dynamic pre-emphasis employed during recording, plus a form of dynamic de-emphasis used during playback, that work in tandem to improve the signal-to-noise ratio. As a result of their narrow tracks and slow speed, cassettes make tape hiss a very severe problem. Cassette tapes were originally designed to trade off fidelity for the convenience of recording voice by using a very narrow tape running at a very slow speed of 1⅞ inches per second (ips) housed in a simple plastic shell when 15 ips or 7½ ips tape speeds were for high fidelity, and 3¾ ips was of lower fidelity. Other solutions are to run the tape at a higher speed or use a wider tape. One solution to this issue is to use low-noise tape, which records more signal, and less noise. When recording a signal on magnetic tape, there is a low level of noise in the background which sounds like hissing. Aside from Dolby HX, all the Dolby variants work by companding: compressing the dynamic range of the sound during recording, and expanding it during playback. Dolby B, C, and S were designed for the consumer market. Of the noise reduction systems, Dolby A and Dolby SR were developed for professional use. It is common on high-fidelity stereo tape players and recorders to the present day, although Dolby has as of 2016 ceased licensing the technology for new cassette decks. The first was Dolby A, a professional broadband noise reduction system for recording studios in 1965, but the best-known is Dolby B (introduced in 1968), a sliding band system for the consumer market, which helped make high fidelity practical on cassette tapes, which used a relatively noisy tape size and speed. A Dolby 361 A-type noise reduction module Dolby noise-reduction system Product typeĪ Dolby noise-reduction system, or Dolby NR, is one of a series of noise reduction systems developed by Dolby Laboratories for use in analog audio tape recording.
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