closed loop system

Here d = disturbance & n = noise

  • \$\begingroup\$ '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. \$\endgroup\$
    – Chu
    Mar 3, 2017 at 9:17
  • 2
    \$\begingroup\$ "d" is multiplied by "P" hence it has to be different to "n". \$\endgroup\$
    – Andy aka
    Mar 3, 2017 at 9:59

3 Answers 3


According to your image, disturbance acts on a controller output, while noise acts on a process output.

Take a moving vehicle for example - obstacle on the road would be a noise, and some (unexpected) event in the engine, gas tank etc. (in a car itself) would be a disturbance.

  • \$\begingroup\$ ....and the transfer functions y/d resp. y/n will be different. \$\endgroup\$
    – LvW
    Mar 3, 2017 at 8:28
  • \$\begingroup\$ @Marko Gulin Thanks for answer. Can you tell me what are the differences between noise & disturbance in general? \$\endgroup\$
    – basic123
    Mar 3, 2017 at 8:45
  • \$\begingroup\$ The main difference is where they act on a system (before or after a process). Both disturbance and noise are (usually) unpredictable, and they are usually modelled as a stochastic process. \$\endgroup\$ Mar 3, 2017 at 10:14

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\$.


MrYouMath's answer is the most accurate. In a Control System, Disturbance is what you make the control system for in the first place, it can be anything that alters the functionality of whatever you are working with. If it's a car, you could say that a disturbance is an obstacle in the road, or if it's a washing machine, it could be a weight overload. Noise here refers to electrical noise, it's an alteration in the output which in that particular control system that your image shows, is mitigated with a feedback loop


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.