Disabilities: Disabilities such as hearing loss, impaired vision, mobility problems or speech impairment can affect the effective communication. Proper communication method should be known and pre-aware of before communicating the people with disability or different health issues.
Cultural Differences: Communication differences can result from differences in culture. In some cultures, children are not allowed to speak in front of adult and some kind of body gesture, eye contact, facial expression and touch are inappropriate.
Environment: Environment is one of the most important factor to consider as well. Ensure the lights, air, temperature, noise, crowd, safe and comfortability in correct measure before establishing effective communication.