| Abstract from DBPedia | Noise reduction is the process of removing noise from a signal. Noise reduction techniques exist for audio and images. Noise reduction algorithms may distort the signal to some degree. Noise rejection is the ability of a circuit to isolate an undesired signal component from the desired signal component, as with common-mode rejection ratio. All signal processing devices, both analog and digital, have traits that make them susceptible to noise. Noise can be random with an even frequency distribution (white noise), or frequency-dependent noise introduced by a device's mechanism or signal processing algorithms. In electronic systems, a major type of noise is hiss created by random electron motion due to thermal agitation. These agitated electrons rapidly add and subtract from the output signal and thus create detectable noise. In the case of photographic film and magnetic tape, 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 ferric oxide or magnetite), 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.ノイズリダクション (Noise reduction) とは、音声や映像などといった信号に含まれるノイズを抑圧・軽減する、信号処理の一種である。 使われる場所・目的はさまざまであるが、主なものとして、撮像素子を高感度で使用した場合に混入を避けられない熱雑音などが発生源のノイズを取り除く、というような原信号を改善するタイプのものと、アナログ磁気記憶において避けられないヒスノイズを軽減するために、記録時に原信号を強調するような変換を掛けておき、再生時にノイズもろとも逆変換を掛けることで、録音再生によるノイズを軽減するタイプのものがある。 (Source: http://dbpedia.org/resource/Noise_reduction) |
