It deals with the efficient coding of his speech signal so that speech or sound can be transmitted at low transmission rate over networks. The goal of sound transmission is to provide the speech quality to the receiver as was generated at the receiver as was generated at the sender side. For the transmission of speech the given four steps are used they are:

Signal form coding:

To achieve the must efficient coding of the audio signal, the data rate of a PCM coded stereo audio signal with CD quality requirement is
Rate = 2*(44000/sec)*(16bit/8bit per byte) = 176400 bytes /sec = 1411200 bit/sec.
The telephone quality needs only 64 kb/sec. to transmit the CD quality signal over telephone the rate of it should be lowered or it difference pulse code modulation can be used to get the data rate to 56 kbps.

Source coding:

Parameterized system work with source coding algorithm, Here the specific speech characteristics are used for data rate reduction.

The signal is split into a collection of frequency channels because only certain maxima are relevant to speech. The differences between voiced and unvoiced sounds are considered into account. Voice less sounds are simulated by the noise generator and for the voiced sounds, the simulation comes from a sequence of pulse the data rate of 3 kbps can be generated with a channel encoder but quality is not always satisfactory.

Recognization:

Speech Recognization (analysis) occurs on the sender side and speech synthesis or generation occurs on the receiver side only the characteristics of the speech elements are transmitted that is middle frequency bandwidth are the speech elements. For it frequency bandwidths are used in the corresponding digital filter with brings the data rate down to 50 bits per seconds.

Achieved quality:

The fundamental goal for speech and audio transmission with respect to multimedia system is how to achieve the minimum data rate for a given quality. The quality of speech depends on the data rate as well as the quality of audio depends on the number of bits per sample value.
For speech quality the data rate of 8 kbps can be used in telephone quality standard and CD quality can be achieved with reduction from 16 bits per sample value to 2 bits per sample value that is only 1/8th of actual data needs to be transmitted.