The voice is probably the most important tool of the presenter. It carries most of the content that the audience takes away. One of the oddities of speech is that we can easily tell others what is wrong with their voice, e.g. too fast, too high, too soft, etc., but we have trouble identifying and adjusting our own voices.
There are three main qualities when we talk about vocal abilities:
Volume: How loud the sound is. The goal is to be heard without shouting. Good speakers lower their voice to create anticipation and draw the audience in. They will raise it to emphasize a point.
Tone: The characteristics of a sound. A tuck has a different sound than leaves being rustled by the wind. A voice that carries fear or intimidation can frighten the audience, while a voice that carries laughter or light-heartedness can get the audience to smile.
Pitch: How high or low a note is. From personal experience, a high pitched voice tends to command less attention from the audience.
Pace: This is how long a sound lasts. Talking too fast causes the words and syllables to be short, while talking slowly lengthens them. You should aim for a balanced pace. You can also vary your pace to maintain the audience's interest.
There are two good methods for improving your voice:
1. Listen to it! Practice listening to your voice while at home, driving, walking, etc. Then when you are at work or with company, monitor your voice to see if you are using it how you want to.
2. One good way to listen to your voice is to follow these following steps. Cup your right hand around your right ear and gently pull the ear forward. Next, cup your left hand around your mouth and direct the sound straight into your ear. This helps you to hear your voice as others hear it. It might be completely different from the voice you thought it was!
Now practice moderating your voice.