The sender is you, the person trying to communicate!  Even with great intentions, if you don’t recognize the noise, you can be less effective with your message. 

Encoding is the process of turning thoughts into communication. If you think "I have to give them some bad news", you must encode it in a way that will be helpful.

Noise is anything that reduces the clarity of the message, just as it's hard to hear a low volume news video in a room full of loud conversation.  Noise is a barrier or attenuator to effective communication.

Noise examples:

• Environmental noise (example above)
• Physiological-impairment noise (hunger, fatigue, headache)
• Semantic noise (different understandings of a word)
• Syntactical noise (mistakes in grammar)
• Cultural noise (assumptions about a culture, or true cultural beliefs that conflict with message)
• Psychological noise (stress, anger, or sadness in the moments of communication)