HOW AUDIO CODEC DO ON MOUTHPIECE, EARPIECE, IHF SPEAKER OR BUZZER AND VIBRATOR ON MOBILE PHONE CIRCUITS

The Audio Codec is a circuit that controls sound signals in a cellphone circuits. It acts like an audio amplifier or an audio mixer or a sound booster.
Audio codec is the main area in a mobile phone where all audio properties is being process, during transmission and receiption. It converts the sound signal into radio frequency signal, and also converts radio frequency signal into a sound signals.
Like for example a microphone's sound signal is being amplified then converts and feeds to radio frequency before it send to the network airwaves. Opposite to that process is the conversion of radio frequency into an audible or understandable sound, and that sound is that what we hear on the earpiece speaker.
A typical block diagram below show  how audio interfaces being connected to anaudio codec circuit.

The Audio codec is the main part which control all audio properties from all audio interfaces like the microphone, earpiece, IHF (integrated hands free) speaker or a buzzer, ringer, head set and vibrator motor. A typical audio circuit is being filtered from any sound interference signal to avoid sound interruptions.