To communicate effectively you need to prevent or reduce the barriers to communcation as much as possible. For example, if you are a presenter in a presentation you have to speak crealy and loud enough without any interference for the audience to hear it properly and won't get distracted.
Background Noise
Background nois can be very distractive even if it is only a whistling noise from an air condition.
Examples: air conditioning, people chatting, mobile phones
Distraction
Distraction is something than can cut the attention of the audience and will affect the presentation.
Examples: ringing mobile phone, people late or leaving unexpectedly
Lack of Concentration
Lack of concentration from the audience can affect them from absorbing information from the presentation
Examples: Boredom (because of the presentation), lack of stimulation
