Channels, noise and coding
Noise: is any disturbance existed in a channel which distorts the signal transmitted. Noise is always harmful to communication.
syntactic noise: makes structural difference between a message sent and the message received (distorted phone call, dissolved ink script).
semantic noise: misinterpretation by ambiguity of a message (bad spelling, inappropriate phrases)
pragmatic noise: is not produced by the sender, but anything else which decreases the readability of a message (a bad radio receiver).