Perceptual barriers are internal. If you go into a situation thinking that the person you are talking to isn't going to understand or be interested in what you have to say, you may end up subconsciously sabotaging your effort to make your point. You will employ language that is sarcastic, dismissive, or even obtuse, thereby alienating your conversational partner.
Think of movie scenarios in which someone yells clipped phrases at a person they believe is deaf. The person yelling ends up looking ridiculous while failing to communicate anything of substance.