The simplest definition is any sound that is unwanted.
'Noise' when referring to any waveform or signal, is interference from other outside sources that contaminates the original signal or waveform....
Thermal noise occurs due to the motion of millions of electrons in a object. Due to the central limit theorem, the total effect can be modeled as a Gaussian distributed random variable with zero mean...
Noise triangle is a triangular noise distribution for FM.Noise triangle is the study of effect of noise on the carrier signal of the FM wave.for more details contact -Ameya Muley...