Noise cancellation is the process of eliminating or reducing the level of background noise in the desired signals in order to improve the sound quality. Clear sound is very important in video conferencing. Sometimes this clearness can be disrupted because of the distortion and background noises. There are two levels of distortion — high and low. Low distortions differ from high ones in that they are more "gentle". Whereas high level of distortion is characterized by severe interference, lengthy, intrusive noise, and complete change of voice signal. The most common disturbances are clicks, wheezing, rumbling, whistling, humming, and buzzing.
Noise can be constant and periodic (pulsating). Constant noise is divided into tonal and broadband. The basic features of tonal noise are buzzing and humming. The main difference between tonal and broadband noise is that the latter has a frequency coloring, but it has no separate band. Broadband noise is characterized by sounds like a whistle and roar. It is necessary to use noise cancellation systems in order to get rid of unwanted noise.
The main objective of noise cancellation is to eliminate and/or reduce noise during a video conference. Most methods of noise cancellation affect the quality of the transmitted sound, but thankfully, modern algorithms are able to modify the audio stream so that minor modifications will not be noticeable to the human ear.
Noise reduction systems are designed for equalization of signal/noise ratio (the ratio of the noise level to the signal). They are used for processing of audio and video signals. There are two types of noise reduction systems: filtering systems, which involve clearing the desired signal of the noise, and systems that convert the signal for transmission across noisy channels.
Noise cancellation systems, unlike noise reduction systems, completely turn off low-frequency amplifiers in the absence of desired signals. There are spectral (disabling the audio amplifier) and amplitude noise cancellers (detect the ratio between desired signal and noise). Today, many manufacturers of equipment for video conferencing are ready to provide their users with devices that combine several useful features. For example, a speakerphone with echo cancellation and noise reduction features. These devices are able to provide a high level of audio comfort even in large rooms.
Author: TrueConf Team