Why Audience can not understand your speech. Read Tips to Prepare for Public Speaking.
* Audience cannot understand your speech when you speak too slowly or too fast.
* You use the language that your audience can not understand.
* Your Audience can not understand your speech when you have English communication barrier.
* When your pronunciation is vulgar.
* You may have bad accent.
* When your ideas may be confusing or very difficult to follow by the Audience.