English is timed by the syllables we stress. It is thus irregular in rhythm, like the two family groups above. Graphic from here.
By Peter McKenzie-Brown
Imagine yourself at public auditions in which four conductors are competing for the top job in an orchestra. Each competitor has to conduct the same piece of music, and each to the same metronome. As he waves his baton, the first conductor begins with the words, “One, two, three, four.” The second says “One and two and three and four.” The next says “One and a two and a three and a four.” And the last aspirant says “One and then a two and then a three and then a four.”
Which of these conductors will miscue the orchestra? The answer is “None.” Each of these four sentences takes exactly the same amount of time to say. This illustrates a key and yet peculiar feature of our language. It is called the stress-timed rhythm of English.
Stress-timing: We can illustrate with almost any word of two or more syllables – for example, “syllable.” We stress this word using the pattern Ooo, placing primary emphasis on the first segment of the word. In English every long word has its own stress pattern. Think of the words “import” and “record,” for example. Both words can be pronounced using either the pattern Oo or the pattern oO. Which pattern you use fundamentally changes the meaning of the word.
Something else happens after you choose which syllable to stress. The pronunciation of the main vowel in the unstressed syllable changes, often to the sound ‘uh’ which is the single most common sound in the English language. This sound has its own special name, schwa, and about 30 per cent of the sounds we make when we speak English are the sound schwa. In English, schwa can be represented by any vowel.
For example, consider the following two-syllable words. The first word uses the stress pattern Oo; the second, the stress pattern oO. You will notice that in each case we pronounce the unstressed vowel as schwa, regardless of its spelling.
A: Atlas; Canoe
E: College; Reveal
I: Cousin; Disease
O: Anchor; Contain
U: Lettuce; Support
This practice of replacing unstressed vowels with schwa also occurs in connected speech – English as we use it in our daily lives. If I ask “Where are you from?” I will stress the word “from,” pronouncing the short ‘o’ sound quite clearly. If you answer “I’m from Sydney,” you will most likely reduce the ‘o’ to schwa. The reason is that you are likely to stress the word “Sydney” instead. This reduction of vowel is the key to the stress-timing of most forms of English.
It's worth noting that some English dialects from India, for example, are characterized by a syllable-timed rhythm. These comments refer to the English of Britain, North America and Australia.
Native English speakers from those countries frequently use schwa in unstressed syllables. This is why it takes the same amount of time to say “One, two, three, four” as it does to say “One and then a two and then a three and then a four.” Reducing vowels enables us to speed through unstressed syllables. This is how we achieve the particular rhythm of English, in which stressed syllables are roughly equidistant in time, no matter how many syllables come in between.
Most of the world's other major languages have quite a different pattern. They are known as ‘syllable-timed’ languages. Each syllable receives approximately the same amount of stress as the others in a word or a sentence. These languages thus have quite a different rhythm from that of English. Think of them as being like this line of soldiers.
Vowels: When we learn to read, our teachers tell us that vowels are the characters a, e, i, o and u. Phonologically, though, a vowel is a speech sound in which the air stream from the lungs is not blocked in the mouth or throat. Usually, when we pronounce vowels we also vibrate our vocal cords.
We form the vowels in our mouths by moving five speech organs around. The most important of those organs is the tongue – language is the “gift of tongues” – and linguists often describe the vowels by the position of the tongue in the mouth. The vowels range from front to back and high to low. For example, the following ‘Sammy diagrams’ show the position of the tongue in the pronunciation of the high back vowel in the word “boot”, the low back vowel in the word “pot”, the high front vowel in the word “beat” and the low front vowel in the word “bat”.
The position of the tongue when we make vowel sounds is illustrated in the Sammies shown to the side and below.
Based on North American pronunciation, the words in the columns give examples of the 12 vowels in common use. Note that the vowel in “pot” is neither fully central nor fully back. The central vowels are essentially schwa, the sound that makes vowel reduction possible.
In English, the high vowels, shifting from high to low, include the vowel sounds in beat, bit, bait, bet and bat. The central vowels are the mid vowels in machine and but. The back vowels, ranging from high to low, are in boot, book, boat and bought. The vowel in pot is an odd one. It is a low vowel, but it is neither fully central nor fully back.
The Sammy diagrams above, plus those that follow, come from the book Teaching American English Pronunciation, by Peter Avery and Susan Ehrlich. Click to enlarge.
Finally, a few graphics showing pronunciation patterns in North American English, also from Avery and Ehrlich.