lets begin… the Basics

30/10/2012 § 1 Comment

Before I start, we need to know some basic stuff.

types of signals

Signal is physical quantity which varies with time.

Here, the first thing that comes to mind is a wave. There are two kinds of waves, electromagnetic waves and mechanical waves. This is a good place to learn more about them. Sound is a mechanical wave and when we are talking about making music from computer, we are – in a general sense – talking about mechanical wave. But we never actually manipulate ‘mechanical wave’, we modify their ‘computer (digital) representation’. We’ll get to that in a minute.

Now that we know that sound is a mechanical wave and we want to manipulate this wave by using a computer. To represent a mechanical wave in a way that computer understands we have to sample it in time and amplitude. This leads us to our next topic.

sampling

Sampling is fairly simple to understand. There are various resources out there to explain it way better than I can. The take-away is ‘The Sampling frequency‘. It’s the frequency at which samples should be taken so as to re-build the original analog wave. Sampling frequency must be more than twice the maximum frequency present in analog signal otherwise aliasing will occur. Generally we over-sample the analog signal so as to re-build analog wave more precisely. In this process there is always loss of information. But  engineers manage to re build initial signal just good enough so that it still makes sense by sampling at sampling frequency.

Sampling in time gives us a signal what we call a ‘discrete signal’. Sampling of amplitude is also done so that computer may store the in coming information, this is generally called quantization. This representation is called ‘digital signal’

This complete process is called analog to digital conversion.

Now, how we get analog back from this representation, here it is.

take aways

  • sampling frequency
  • aliasing
  • digital and discrete signal

I have just brushed the basics. I’ll write more about them in future.

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