In describing the process of communication, experts identify senders or encoders of messages, receivers, or decoders of messages, the channels communicators use to send those messages and the feedback the communicators send back to one another. Noise is identified as anything in the communication process that interferes with the intended receiver getting and understanding the message. There are a variety of internal and external noises, three readily recognised, and a fourth which is less obvious.
Environmental noise is sometimes called physical noise, which means anything that is external to both the sender and the receiver that disrupts the sending or receiving of messages. Examples of physical noise include a stereo playing loudly, a cell phone ringing, the hum of an HVAC unit, being seated far from the speaker, people chatting loudly behind you, cars driving or honking, sunglasses, difficult-to-read fonts or type, poor grammar and pop up ads. These items may prevent the receiver from even hearing or viewing the message, or they may distract the receiver and prevent him from truly attending to the messages.
This kind of noise refers to actual physical barriers within the sender or the receiver that cause messages to have trouble getting through. Hearing loss is a common physiological barrier. Poor eyesight is another. A student in a classroom who needs glasses to see the board from the back of the classroom but refuses to wear glasses experiences physiological noise. Those with other visual impairments such as blindness, memory loss or complete hearing loss have physiological noise in the communication process, as do those who cannot speak clearly or who stutter.
Psychological noise is mental interference between sender and receiver. This includes feelings about the other communicator, such as love, hatred or irritation. It includes other emotions or extreme emotionalism in one of the communicators. There is psychological noise when a communicator has wandering thoughts or is daydreaming, when a communicator has biases or prejudices, or when a communicator is close-minded. Another factor that may create psychological noise is personal difficulties. A recent break-up or relationship problems, death or illness of a close family member, financial worries or the birth of a child can create psychological noise, making it difficult for messages to get through.
Semantic noise is sometimes grouped with psychological noise, but is often defined separately. This disruption in the communication process happens when the sender and receiver understand words differently, and apply meaning to words differently. Some examples of semantic noise include different dialects or languages, a communicator using specialised jargon, or ambiguous, abstract words with several possible meanings. There is a great deal of semantic noise that happens when messages are translated from one language to another -- the direct translation is not always exactly accurate.