What is Noise? Irregular fluctuations that accompany a transmitted electrical signal but are not part of it and tend to obscure it. In Simple words, noise is an unwanted signal that hinders the transmission of other signals. Types of noise : Thermal noise : Thermal noise due to agitation of electrons. It is present in all electronic devices and transmission media and is a function of temperature Intermodulation noise : It occurs if signals with different frequencies share the same medium. Interference caused by a signal produced at a frequency that is the sum or difference of original frequencies. Crosstalk : Crosstalk has been experienced by anyone who, while using the telephone, has been able to hear another conversation; it is an unwanted coupling between signal paths. It can occur by electrical coupling between nearby twisted pairs or, rarely, coax cable lines carrying multiple signals. Effect of noise on transmission signal Signal noise, in its most basic sense, is any unwanted interference that degrades a communication signal. Signal noise can interfere with both analog and digital signals; however, the amount of noise necessary to affect a digital signal is much higher.
