Cardinal vowels are a standard reference system and those people who want to learn phonetics have to learn to make them accurately and of course recognize them correctly. Learning these cardinal vowels is a very useful way of describing, classifying, comparing and understanding vowels.
Cardinal vowels are: /i/, /a/, /ɑ/, /u/, /e/, /ɜ/, /ɔ/, and /o/. Traditionally, cardinal vowels are represented graphically using a quadrilateral shape. I am using here the shape recommended by International Phonetic Association that looks like a kind of trapezoid. The figure can be seen below.
In order to understand the graphical representation of the Primary Cardinal Vowels we have to understand what front, back, close, and open mean.
Let’s consider the English word “see”. Making the /i:/ vowel sound (that is produced by the “ee” from the word “see”) we are able to see (maybe in a mirror if we tilt the head back) that the tongue is held up very close to the roof of the mouth. Now let’s compare this sound with the sound /æ/ made by word “bag” for example. When we make the /æ/ sound, the surface of the tongue is not close to the roof of the mouth. So, we can say that the /i:/ sound is a close vowel sound and the /æ/ vowel sound is a relatively open sound (see the graphical representation of open and close sounds below).
In making the /i:/ and /æ/ vowels, the front part of the tongue is raised. A vowel that is produced by raising the back part of the tongue it is called a back vowel. The vowel /ɑː/ from the word “car” is produced by raising the back part of the tongue. The vowel /u:/ from the word “boot” is also a back vowel but compared with vowel /ɑː/ it is closed.
These 8 vowels represented here are called primary cardinal vowels and they are the most familiar to the speakers of English as a second language (especially for speakers of most European languages). There are other cardinal vowels called Secondary cardinal vowels that sound less familiar.
Cardinal vowel no. 1 has the symbol [i]. This vowel is as close and as front as it is possible to make a vowel without obstructing the flow of air to produce a friction noise (the kind of sound that can be heard in consonant sounds like /s/ or /f/). Cardinal vowel no. 5 has the symbol [ɑ] and is the most open and back vowel that can be made. Cardinal vowel no. 4 has the symbol [a] and it is fully open and front. Cardinal vowel no. 8 has the symbol [u] and it is fully close and back.
These are extreme points as it can be seen in the first image above. After establishing them it is easier to add intermediate points (see vowels no. 2, 3, 6, and 7).
As we have already seen, we can classify vowels according to how close the tongue is to the roof of the mouth and what part of the tongue (front or back) we raise in order to produce the sound. There is another way to classify the vowels and that is the lip-rounding. Human lips are very flexible and they can take so many different shapes and positions but three of them are the most common.
Rounded lips – the corners of the lips are brought towards each other and the lips are pushed forward a little bit. This shape of the lips can be clearly observed making the vowel sound /u:/
Spread lips – the corners of the lips move away from each other. Making the sound /i/ exemplifies the spread lips shape.
Neutral lips – the lips are not noticeable rounded or spread. The schwa sound is a good example of neutral lips shape.
The short vowels in English language are: ɪ, e, æ, ʌ, ɒ, and ʊ. However, these vowels can have different length depending on the context. Each of the short vowels is graphically represented in relation with the cardinal vowels using the same trapezoid shape.
There is another short vowel called schwa but it is different than the vowels mentioned above from many points of view. Because it is different and the most commonly used sound in English the schwa sound will not be discussed here.
The vowel /ɪ/ - The vowel /ɪ/ is in the close front area and it is very similar with the cardinal vowel /i/. However, it is more open and the lips are a little bit spread when producing the vowel sound /ɪ/. It can be seen in words like fish, ship, bit etc.
The vowel /e/ - Lips are slightly spread when producing the vowel /e/. On the graphical representation it is placed just above the cardinal vowel /ɜ/. It can be seen in words like: men, yes etc.
Short vowel /æ/ - This is a front and open vowel. However, it is not as open as the cardinal vowel /a/. The lips are also a little bit spread and the best example of words where the vowel /æ/ can be seen is: cat, gas, bat, bag etc. As the phonetic symbol shows, it produces a sound that sounds like /a/ and /e/ sounds pronounced together at the same time. Some learners of English find this sound extremely difficult to reproduce while for others it is quite easy.
The vowel /ʌ/ - This is an open vowel and it sounds like many sounds produced by the letter “a” in many European languages and also in Vietnamese language. The position of lips is neutral and learners of English find this sound easy to be reproduced. The vowel /ʌ/ can be seen in words like cup, but, some etc.
The vowel /ɒ/ - This is a vowel that creates many pronunciation problems for learners of English. Some pronounce it as an /o/ sound while others pronounce it as an /a/ sound. The truth is somewhere in between and honestly, even native speakers of English, pronounce this sound differently. The vowel /ɒ/ is not fully back and in tongue height it is between open-mid and open. The lips are a little bit rounded and have a great contribution in producing this sound. “Pot” and “gone” are two common words where the vowel sound /ɒ/ can be seen.
The vowel /ʊ/ - There is a big difference between the vowel /ʊ/ and the nearest cardinal vowel /u/. However, in speech, I hardly ever heard a non native English speaker producing this sound. Everybody will use the cardinal vowel /u/ instead of /ʊ/. The vowel /ʊ/ is more open and nearer to central than the cardinal vowel /u/. The lips are rounded when producing the vowel sound /ʊ/. The words “put”, “book”, and “push” are commonly used words containing the vowel /ʊ/.