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Old Oct 23rd 2014, 12:16 AM   #1
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Quantization and Sample Rate

1. What defines a ‘minimum’ sample rate and what (if any) benefit
comes from sampling at higher rates? What happens when we take our samples (pictures, voltage measurements, etc.) at very wide time intervals (low sample rates)? What do we successfully capture? What do we miss? What about shorter time intervals (higher sample rates)?

2. How does bit depth (quantization) affect sound quality and what
determines ‘enough’ bit depth? How much do we need to measure? What might
be considered a ‘bad’ measurement and what problems might come from it? How would we hear a ‘bad’ measurement? What conditions are needed for a ‘good’ measurement and how ‘good’ is good enough?
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Old Oct 30th 2014, 04:08 AM   #2
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The basic idea is how many discrete points are required before we can't distinguish discrete points any more and it looks (or sounds) continuous.

The basic limit of human hearing is generally quoted as 20Khz (20,000 cycles per second).
To capture this you need (at least) twice as many samples per second (so you get at least 2 points per cycle)

This is the basic theory for pure sinusoidal sound waves.
More complicated wave shapes can be made up from superimposing lots and lots of sine waves.
While it is true that the standard ear can only distiguish upto 20Khz as a pure sine wave, there is some evidence that we can distiguish the change in waveform shape due to the overtones from higher frequencies.
This is (one reason) why some audiophiles still prefer the anolog vinyl records to digital CDs.

Have a look at this wikipedea page:
http://en.wikipedia.org/wiki/Aliasing
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