The answer is interference.
Messages refer to the content or information that is being communicated by the speaker to the audience. This does not fit the examples given, as coughing or walking late are not part of the intended content of the speech.
Interference, also known as noise, refers to any external or internal factors that disrupt the communication process. Examples include someone coughing in the audience or walking in late during a presentation, which can distract both the speaker and the audience, thereby hindering the effective transmission of the message.
The channel is the medium through which the message is delivered, such as spoken words, written text, or visual aids. The examples provided do not pertain to the medium of communication.
Feedback is the response from the audience to the speaker, which can be verbal or non-verbal. While feedback is an important part of the communication process, it does not describe the disruptive actions mentioned in the question.