Do all the signals in real world ,that are of interest in engineering(for measurements or processing)are only continous/analog or there any other alternatives also? For example birds make voice,animals make voices are examples of continous signals

Few natural discrete signals in my opinion Number of teeth and number of bones in human Number of mountains in a range,height of a mountain/hill Please kindly give me other examples from natural world

Please kindly guide me if i am wrong in my understanding of continuous and discrete signals

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    $\begingroup$ I think you like asking "does this exist in real world", for some reason. It's not really a meaningful thing to ask, still: A mathematical model is a real-world thing. And if it as much as describes a physical entity well enough for some purpose, then that physical entity, by all practical means, fulfills the properties of the model. That's what the model is for! So, whenever you ask "Does {mathematical concept} exist in real world?", the answer will always be, "yes, because {mathematical concept} exists!". $\endgroup$ Apr 5, 2020 at 23:32
  • $\begingroup$ ... and your previous questions all illustrate that very well. So, maybe the next time when you feel like asking "Does {mathematical concept} exist in the real world?", you should ask yourself "Ok, if it exists, what is an example that I can describe using {mathematical concept}." That answers the first question, and then, much more actionable/interesting questions may arise! $\endgroup$ Apr 5, 2020 at 23:34

2 Answers 2


Eventhough most engineering signals are continuous, not all are such. For example, statistics of many kinds provide discrete data such as daily stock market indicators, computer network stats, hourly number of customers in a queue, etc...

Of course, audio signals are transmitted as acoustic pressure waves through air (typically) and pressure is a continuous modeled physical variable.

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    $\begingroup$ The number of photons hitting my camera sensor pixel, number of alpha decay processes observed in a given timeframe, number of maxima in an interference pattern, the lottery draw, the "next number" display at the tax office, … soooo many examples! $\endgroup$ Apr 5, 2020 at 23:49
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    $\begingroup$ @MarcusMüller Hi Marcus ! $\endgroup$
    – Fat32
    Apr 6, 2020 at 2:27
  • $\begingroup$ @MM almost all the examples mentioned by you are discrete? $\endgroup$
    – DSP_CS
    Apr 6, 2020 at 6:58
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    $\begingroup$ yes, exactly, not almost, but all of them are value-discrete, some also time-discrete. You asked whether signals in the real world are all continuous; I delivered counter-examples (as an example of the mental gymnastics I recommend in such situations as yours: try to find examples and counterexamples of your hypothesis), thereby further giving an answer to your question: no, not all physical things are continuous. $\endgroup$ Apr 6, 2020 at 7:16
  • $\begingroup$ @Fat32 please kindly check the updated question statement, where i tried to put my understanding in a more detailed manner especially in regards to natural signals $\endgroup$
    – DSP_CS
    Apr 6, 2020 at 8:17

Signals can be continuous/discrete in either time, in value or both. Discrete values are quite common in physics. For example if you roll a die, it will come up facing one side up. So it's 1,2,3, 4, 5, or 6 but nothing else.

Time discrete signals are certainly uncommon in macroscopic physics (i.e. no quantum mechanical effects).

Of course, signals do not need to be a function of time, they can also be a function of space, temperature, or any other suitable physical quantity. It you manage to construct a value-discrete signal that's a function of a value discrete variable, you have created a real world digital signal.


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