Pitch is the auditory attribute of sound ordered on a scale from low to high. You can think about the notes on a musical score with pitch getting higher as you move up the scale.
Pitch is closely related to frequency of sound waves; it is almost entirely determined by how quickly the sound wave is making the air vibrate and has almost nothing to do with the intensity, or amplitude, of the wave, which relates to.
That is, "high" pitch means very rapid oscillation, and "low" pitch corresponds to slower oscillation.
As a speaker you want to find a pitch that is suitable for speaking. Generally, you want to use a pitch range that would normally be comfortable for your natural conversation.
For men and women, the size difference of the vocal folds, reflecting male-female differences in larynx size, will influence available pitch range.
Adult male voices are usually lower-pitched and have larger folds. The male vocal folds are between 17mm and 25mm in length. The female vocal folds are between 12.5mm and 17.5mm in length.
The pitch or pitch contour in which a syllable is pronounced conveys shades of meaning such as emphasis or surprise, or distinguishes a statement from a question.
All languages use pitch pragmatically as intonation (or inflection as is used in some texts) to communicate different meanings—for emphasis, to convey surprise or irony, or to pose a question.
Generally speaking, there are four types of pitch changes you can make, as follows:
Consciously or unconsciously the speaker will use the different patterns of pitch to convey different meanings to the listener.
Consider the uses of pitch change and the associated meanings in the different categories as follows:
Informational: for example, "I saw a ↘man in the garden" answers "Whom did you see? " or "What happened? ", while "I ↘saw a man in the garden" answers "Did you hear a man in the garden?"
Grammatical: for example, a rising pitch turns a statement into a yes-no question, as in "He's going ↗home?"
Illocution: the intentional meaning is signaled by the pitch pattern. For example, "Why ↘don't you move to California? " (a question) versus "Why don't you ↗move to California? " (a suggestion).
Attitudinal: high declining pitch signals more excitement than does low declining pitch, as in "Good ↗morn↘ing" versus "Good morn↘ing."
Textual: information not in the sentence is signaled by the absence of a statement-ending decline in pitch, as in "The lecture was canceled" (high pitch on both syllables of "cancelled", indicating continuation); versus "The lecture was can↘celed." (high pitch on first syllable of "canceled", but declining pitch on the second syllable, indicating the end of the first thought).
In public speaking you can apply changes in pitch not only to a single word such as an exclamation, "Oh!" but to any group of syllables, words, and even sentences to convey different meanings. You can change pitch of successive syllables in a word, word groups, or successive sentences. You want to make sure that you use pitch to convey the intended meaning so that you do not drop the pitch, for example, until you have completed an idea.
Additionally, in natural conversation pitch changes make some words stand out more than others, you can do the same in your public speaking for emphasis. You can use pitch to draw the listeners' attention to words or phrases that are more important than others. When speaking you will naturally use a range of pitches to convey different meanings.
1. Avoid monotony, speaking with one pitch tone or little variety in pitch. Make sure to vary the speech as you speak to show emphasis and change in meaning.
2. Practice saying sentences with different intonation patterns to change the meaning. For example, if you make a statement with falling intonation at the end, you can turn it into a question by raising the intonation at the end. Try for example, "See what I mean," and "See what I mean? "
Source: Boundless. "Pitch." Boundless Communications Boundless, 14 Mar. 2017. Retrieved 31 May. 2017 from https://www.boundless.com/communications/textbooks/boundless-communications-textbook/delivering-the-speech-12/effective-vocal-delivery-64/pitch-255-4173/