# What is difference between noise and disturbance in control system?

Here d = disturbance & n = noise

• 'Noise' generally refers to measurement noise, possibly Gaussian noise generated in a sensor. 'Disturbance' is normally some unwanted variation of a control signal, for example a step change in ambient conditions. – Chu Mar 3 '17 at 9:17
• "d" is multiplied by "P" hence it has to be different to "n". – Andy aka Mar 3 '17 at 9:59

Noise $n$ affects your meassurements of $y$, so that instead measuring $y$ you will measure $y+n$. Disturbance affects the generation and not the meassurement of the variable $y$.