Intelligent Sound

Noise reduction is a process in which the noise is removed from any given signal. Techniques for noise reduction are theoretically very alike in spite of the signal being processed. However, a complete understanding of the characteristics of a predictable signal could mean the utilization of these techniques differ significantly on the basis of the type of signal.

Uses:

All the recording devices, digital or analogue, possess qualities which make them vulnerable to noise. In all electronic recording devices, a key variety of noise is “hiss” which is caused by unsystematic electrons that, profoundly affected by heat, drift from their chosen path. These wandering electrons manipulate the voltage of an output signal and hence produce noticeable noise.

In the cases of magnetic tapes and photographic films, noise may be introduced because of the grain structure of the medium. In a photographic film, the magnitude of the grains in that particular film decides the film's compassion. More compassionate films have bigger grains. In a magnetic tape, the bigger the grains of the magnetic particles, the more is susceptibility of the medium to the noise. To balance this, bigger areas of a film or a magnetic tape can be utilized to reduce the noise to a tolerable level.

Dbx and Dolby noise reduction systems:

The first commonly utilized audio noise reduction technology was invented by Ray Dolby in the 1960s. Proposed for proficient utilization, Dolby A used to be a kind of decode/encode system wherein the amplitude of the frequencies in four bands was augmented while recording. Then it was reduced proportionately throughout playback. The Dolby B was a uni-band system invented for consumer products. Especially, while recording for the quiet portions of audio signals, the frequencies over 1 kHz would be enhanced. Once it was played back, the procedure would be inverted by the decoder, which would effectively dip the noise level by close to 10dB. The Dolby B system wasn’t as effective as the Dolby A. However, it had the advantage of remaining audible and distinguishable on playback systems in the absence of a decoder.

Dbx was the other analog noise reduction system invented by dbx laboratories. Dbx worked across the whole audible bandwidth. Unlike Dolby B, it was not viable as an open ended system. However, it could attain close to 30 dB of noise reduction. As analog video recordings make use of frequency modulation for luminance, audio style noise reduction is pointless.