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For the reduction of a sound's volume, see. For the noise reduction of machinery and products, see. Noise reduction is the process of removing from a. All signal processing devices, both and, have traits that make them susceptible to noise. Noise can be random or with an even frequency distribution, or frequency dependent noise introduced by a device's mechanism or signal processing.
In recording devices, a major type of noise is hiss created by random motion due to thermal agitation at all temperatures above absolute zero. These agitated electrons rapidly add and subtract from the of the output signal and thus create detectable noise. In the case of and, noise (both visible and audible) is introduced due to the grain structure of the medium. In photographic film, the size of the grains in the film determines the film's sensitivity, more sensitive film having larger sized grains. In magnetic tape, the larger the grains of the magnetic particles (usually or ), the more prone the medium is to noise. To compensate for this, larger areas of film or magnetic tape may be used to lower the noise to an acceptable level. Many noise reduction algorithms tend to alter signals to a greater or lesser degree.
The local signal-and-noise orthogonalization algorithm can be used to avoid changes to the signals. Contents • • • • • • • • • • • • • • • • • • • • • • • • • • • • In seismic exploration [ ] Boosting signals in seismic data is especially crucial for seismic imaging, inversion, and interpretation, thereby greatly improving the success rate in oil & gas exploration. The useful signal that is smeared in the ambient random noise is often neglected and thus may cause fake discontinuity of seismic events and artifacts in the final migrated image. Pro Tool Full Version. Enhancing the useful signal while preserving edge properties of the seismic profiles by attenuating random noise can help reduce interpretation difficulties and misleading risks for oil and gas detection. In audio [ ]. Example of noise reduction using with 0, 5 dB, 12 dB, and 30 dB reduction, 150 frequency smoothing, and 0.15 seconds attack/decay time.
Chuzzles Full Version. Problems playing this file? When using tape recording technology, they may exhibit a type of noise known as. This is related to the particle size and texture used in the magnetic emulsion that is sprayed on the recording media, and also to the relative tape velocity across the. Four types of noise reduction exist: single-ended pre-recording, single-ended hiss reduction, single-ended surface noise reduction, and codec or dual-ended systems. Single-ended pre-recording systems (such as ) work to affect the recording medium at the time of recording. Single-ended hiss reduction systems (such as or ) work to reduce noise as it occurs, including both before and after the recording process as well as for live broadcast applications.
Single-ended surface noise reduction (such as and the earlier SAE 5000A and TNE 7000) is applied to the playback of to attenuate the sound of scratches, pops, and surface non-linearities. Dual-ended systems have a pre-emphasis process applied during recording and then a de-emphasis process applied at playback. Compander-based noise reduction systems [ ] Dual-ended noise reduction systems include the professional systems and by, and by, Donald Aldous' NoiseBX, ' () and 's () as well as the consumer systems,, and,, Telefunken's and 's, 's (), 's ()) and, 's, and the Hungarian/East-German system. These systems have a pre-emphasis process applied during recording and then a de-emphasis process applied at playback. The first widely used audio noise reduction technique was developed by in 1966. Intended for professional use, Dolby Type A was an encode/decode system in which the amplitude of frequencies in four bands was increased during recording (encoding), then decreased proportionately during playback (decoding).
The Dolby B system (developed in conjunction with ) was a single band system designed for consumer products. In particular, when recording quiet parts of an audio signal, the frequencies above 1 kHz would be boosted. This had the effect of increasing the signal to noise ratio on tape up to 10 dB depending on the initial signal volume. When it was played back, the decoder reversed the process, in effect reducing the noise level by up to 10 dB. The Dolby B system, while not as effective as Dolby A, had the advantage of remaining listenable on playback systems without a decoder.
Was a competing analog noise reduction system developed by, founder of laboratories. It used a root-mean-squared (RMS) encode/decode algorithm with the noise-prone high frequencies boosted, and the entire signal fed through a 2:1 compander. Dbx operated across the entire audible bandwidth and unlike Dolby B was unusable as an open ended system. However it could achieve up to 30 dB of noise reduction.
Since analog use frequency modulation for the luminance part (composite video signal in direct colour systems), which keeps the tape at saturation level, audio style noise reduction is unnecessary. Dynamic noise limiter and dynamic noise reduction [ ] Dynamic noise limiter ( DNL) is an audio noise reduction system originally introduced by in 1971 for use on. Its circuitry is also based on a single. It was further developed into dynamic noise reduction ( DNR) by to reduce noise levels on long-distance. First sold in 1981, DNR is frequently confused with the far more common.