Prosodic features
A
The prosodic (or suprasegmental) characteristics of speech are those of pitch, loudness and speed (or tempo, or speech rate; its inverse is the duration of the constituent segments). These combine together to make up the rhythm of speech, and are combined in turn with stretches of silence (pause) to break up the flow of speech.
To some extent prosodic characteristics are the same in all languages. It is probably true of all human societies that speakers speed up when they are excited or impatient and slow when they are being thoughtful or weighty. We all speak more quietly than normal when we do not wish to be overheard. We all have to speak more loudly to be heard over a distance or in noisy conditions (unless, of course we can use modern technology to transmit and amplify the signal for us).
But it is clear that different languages also regularly differ in their prosodic characteristics. Simply transferring the prosodic patterns of one's mother tongue or L1 to a foreign language or L2 (such as English) contributes to making you sound foreign, and may quite possibly lead to your being misunderstood by other speakers
B. Stress
Stress is realized by a combination of loudness, pitch and duration. Some languages use stress placement lexically (=to distinguish between different words in the dictionary). For example, the Greek words ???['poli] and ???[po'li] differ in meaning. The first mean 'city', the second means 'much, very'. The difference of meaning depends entirely upon the location of stress, and involves no difference in the consonant and vowel sounds. Other languages do not use stress lexically: in French there are no pairs of words of different meaning distinguished by stress placement.
In English there are a few pairs of words distinguished by stress, for example 'billow and 'below or 'import (noun) and im'port (verb). However, the English habit of weakening unstressed vowels means that most pairs of words differing in stress often also have differences in their vowel sounds, so that the distinction is not carried by stress alone. Nevertheless, English is, like Greek, a stress language: stress is an important part of the spoken identity of English word.
A complication factor is that differences of stress in English are largely signaled by pitch movements, as discussed in chapter 2 and 5 below.
C. Tone
Tone is another prosodic characteristic, being realized mainly by differences in pitch of the voice (e.g. high level, mid level, low level, rising or falling). A high pitch results from the relatively rapid vibration of vocal folds in the larynx, a low pitch from a relatively slow vibration. An acceleration in the rate of vibration is heard as rising pitch, a slow down as a falling pitch. In a level pitch the vocal folds vibrate at a constant rate.
Some languages use tone lexically. For example, in Thai the syllable [kha:] has different meanings depending on the tone with which it is said. With tone 1 (a mid level tone) it means 'to be stuck'. With tone 2 (low level) it is the name of a plant, 'galingale'. With tone 3 (falling) it means 'value', with tone 4 (high level) 'to trade', and with tone 5 (rising) 'leg'. In Mandarin Chinese, [ma] with tone 1 (high) means 'mother', with tone 2 (rising) 'hemp', with tone 3 (low fall-rise) 'horse', and tone 4 (falling) 'to cold'.
...(other examples of languages use tone lexically).