One important thing with learning to do presentations is that you have to work with what you have. Most people cannot completely change their character when they do a presentation, and they certainly can't change their appearance or voice. However, there are some small adjustments you can make to maximize your basic characteristics. On this page we will look at how to do this with your voice.
If you're not using a microphone, your voice should be loud enough for the people furthest away from you to hear comfortably. The best way to judge this is to look at them as you talk. If they seem to be struggling to hear, you need to speak louder. If you're really not sure, you can always ask: "Can you hear me OK at the back?"
For most people presenting in their first language, it is best to slow down your speech from your normal speaking rate a little (10-20%) when giving a presentation. If you are presenting in your second language, it depends on your fluency. Very fluent, fast speakers should slow down, but slower or hesitant speakers will need to practice to get more fluent so that the audience is not frustrated waiting for the next words. The best way to decide what you need to do is to give a practice presentation to some friends and get their feedback.
Also, rather than really slowing down to be understood, use longer pauses between sentences instead. This gives the audience time to process what you said.
First of all, it is fine to have an accent. Everyone does! And some native accents are more difficult to understand that non-native ones, so don't be worried about speaking English as a second language in a presentation.
However, you should make sure you speak clearly in a presentation. Practice projecting your voice to the back of the room. As we said above, slow down your speaking and try to say each word separately and clearly. And make sure that the audience can see your lips as much as possible.
Pronunciation-wise, there are two things to check. Firstly, if you have new or difficult words in the presentation, make sure that you have practiced saying them until you are quite fluent. Secondly, try to practice your presentation to a friend or family member and get their feedback on anything they don't understand or they think is mispronounced. Listen to their feedback and practice until you get it right. Most online dictionaries and translators have audio so that you can hear how it should be pronounced.
While presentations may cause you some emotional stress (sorry!), there is another kind of stress that you should try to include in your presentation. In English, you'll notice that the important word or words in a sentence are spoken with slightly more force and often in a higher tone. This is called stress.
Note that stress is actually placed on the stressed syllable in a word, rather than the whole word. So if we wanted to stress the word "warming" in a sentence, we might say "We need to STOP the planet from WARM-ing." (Stress is marked here in CAPITALS). Stressing the important words in each sentence helps the audience to understand, and also helps your voice to be more interesting.
Related to stress is intonation (the way your voice goes up and down). In non-question sentences, your voice should go up on the stressed words (or syllables), and gradually fall until the next stressed word or the end of the sentence. Intonation works differently in questions. There is too much to explain here, but if you're curious, you can check this page for more information.
With both stress and intonation, it's maybe better not to focus too much on the rules. But if you have a sentence that you want to sound good, there are many online resources that will turn text to realistic speech for free. Here is one example. Type in what you want to say, and then listen to the output paying attention to the way the voice rises and falls. Then try to copy until you can say it with similar stress and intonation