• Sound is produced when objects vibrate producing pressure waves that can be picked up by humans ear.

• This pressure waves moves in a pattern called as waveform.

• If we graph the motion of waves over time, we get curve of waveforms.

• We can say that sound is stored in form of waves, also called as analog signals or continuous variable signals.

• When sound is needed to be used in any computer application, audio waves are converted to digital form by A-D converter.

• An A-D converter receives electrical voltage as i/p (from the microphone) and generates binary number as o/p (stream of 0’s and 1’s).

• The A-D conversion process takes place in three steps namely; Sampling, Quantization and Coding.

Sampling:

• The process of converting continuous time in to discrete values is called sampling.

• The time axis is divided in to fixed intervals.

• The reading of each value of analog signal is taken for each time interval.

Quantization:

• The process of converting continuous sample values into discrete values is called quantization.

• In this process we divide the signal range into a fixed number of intervals.

• Each intervals is of same size and is assigned a number. These intervals are numbered between 0 to 7.

• Each sample falls in one of the intervals and is assigned that interval's number.

Coding:

• The process of representing quantized values digitally is called coding

• In our example, eight quantizing levels are used. These levels can be coded using 3 bits if the binary system is used, so each sample is represented by 3 bits.

• The analog signal is represented digitally by the following series of binary numbers: 001, 011, 100, 100, 010, 001, 011, 110, and 110.