A/D Digital Measurements


Tutorial Home >Music and Video >Digital Music >CD-ROM Authoring >How do I learn how rate defines the frequency response of analog converters?
Tutorial Home >Music and Video >MP3s >CD-ROM Authoring >How do I learn how rate defines the frequency response of analog converters?
Tutorial Home >Music and Video >Digital Music >CD-ROM Authoring >Digital to Analog Converters >A/D Digital Measurements
Tutorial Home >Music and Video >MP3s >CD-ROM Authoring >Digital to Analog Converters >A/D Digital Measurements

  Step 1:  Measuring the Voltage

Open a Report
When the A/D converter measures the instantaneous voltage appearing at the analog input, it represents this voltage as a number.
  Step 2:  Binary Numbers

Binary Numbers (0,1) are used because they are easy to represent in a circuit as "Off" (0) voltage or "On" (1) voltage.
  Step 3:  Word

A string of Binary digits or bits constitutes a "Word" and the number of bits in a Word is called a "Word Length".
  Step 4:  Full-Scale Digital Audio

The highest amplitude which can be represented with a given word-length is when every binary digit is a "1". An example of this would be 1111111111111111 for 16-bit word.
  Step 5:  What's The Point?

When the A/D converter measures an analog voltage that exceeds its digital ceiling (when the amplitude is out of the measurement range of the converter), a horrible, harsh digital sound occurs.
  Step 6:  Dynamic Range

The difference in level between the loudest signal and the noise floor constitutes the Dynamic Range. A 16-bit system has a dynamic range of about 96db. A 24-bit system has a dynamic range of 144db. However, it is arguable whether we can actually hear 144db, or whether an actual piece of audio equipment can deliver it.
  Step 7:  Quantization

A digital signal's word length will determine the size of the smallest difference in level you can capture, which directly influences the perceived quality of the recording. Quantization in digital audio refers to the tiny incremental step in digital level between a zero and a one. The number of bits determines the size of the steps, the smallest step being the difference between the smallest, and the least significant bit being set to zero and to one.
  Step 8:  A Quantization Analogy

To better define Quantization, use this analogy: If you were to measure a tree and your only form of measurement was a meter, you could probably take an accurate measurement of the tree. However, if you were measuring a small bird and you couldn't use a smaller measurement than a meter, you would be limited to the accuracy of your measurement. The bird would either measure 0 or 1 meter -- quite a gap in the accuracy factor. Now, use this analogy when it comes to sound quality!
  Step 9:  The Bottom Line

Now that your mind is filled with all of this technical jargon, let's simplify things. Keep in mind that the sample rate defines the frequency response and the word length determines the detail (resolution). The more bits, the lower the noise floor and the subtler are the nuances of level changes.