When we talk about front and back vowels in the vowel chart, does it refer to the position of the tip of the tongue or the whole body of the tongue?

Question

This question came to me when I was trying to distinguish between [a] and [ɑ]. The former exists in my native language and the latter is the one that I'm trying to form. My question is: Since it is a back vowel does it mean that I pull the entire body of my tongue towards back? I do not think so because in an explanation that I read somewhere it said that every vowel in the IPA chart can be technically made while still keeping the tip of your tongue fixed behind the bottom teeth.

My problem is that I can only form [ɑ] if I round my lips a little bit, meaning that I can't make the [ɑ] sound with my lips as neutral as when I'm making the [a] sound. And I know this is wrong because [ɑ] is supposed to be an unrounded vowel as well. Most of the vowel charts I have seen on the internet don't actually talk about the tongue position or where the tongue should actually be so I am very confused.

Answer 1

The articulatory definition of front and back vowels (i.e. the definition based on where the tongue is in the mouth) is based on the location of the constriction—that is, the place where the vocal tract is narrowest. This can involve different parts of the tongue depending on the vowel.

However, this articulatory definition turns out not to be ideal, because e.g. it implies going from [i] to [u] is basically the same as going from [æ] to [ɑ], and it's not, really. The human tongue is versatile, but it needs to do different things to make constrictions in different places, and it's not as simple as just measuring the coordinates of the constriction and telling your own tongue to replicate that.

So nowadays, the horizontal axis on the IPA chart is usually defined in terms of acoustics (i.e. the actual sound waves) instead. This suggests that the best way to learn a new "cardinal vowel" (one of the vowels at the extremes of the IPA chart, like [ɑ]) is to listen to recordings of a trained phoneticist saying it, and try to replicate their sound. Knowing that your tongue should be lowered and the articulation should be toward the back of the mouth helps, but that description isn't necessarily enough in and of itself to teach you what exactly your tongue should be doing here.

Answer 2

The general belief is that "front" and "back" refer to the position of the tongue given hypothetical x-ray crosshairs, although actually (computed) vowel charts don't actually display tongue position, they display one of a small number of acoustic relations between formants. Furthermore, most vowel charts (e.g. as found in JIPA sketches) are based on (subjective) auditory analysis, not computed acoustic analysis. So the relationship between front / back or the various vowel heights on a typical vowel chart is only remotely related to tongue position. It's not that all of the tongue has to move up or down, front or back, it's about where the main narrowing is in the vocal tract.

As a starting point, you can consult the collection of expert IPA productions here. The letter <a> is widely used indiscriminately for "the low vowel". If in your language that vowel is more centralized (which is often the case), linguists will usually use <a> anyway because IPA letters describe a range of values, not a precise value. It may be that in order to achieve a satisfactory acoustic output, you have to round your lips a bit to further lower F2.

There is also a physiological factor, that to maximally retract and lower the tongue, it is natural to lower the jaw, which results in quasi-rounded lips (you can overcome this by actively spreading the lips).

Answer 3

I'll answer the Original Poster's question head on:

In relation to the description of vowels, the labels ғʀᴏɴᴛ and ʙᴀᴄᴋ notionally relate to which part of (the body of) the tongue is raised closest to the roof of the mouth: the 'front' or the 'back.' They don't relate terminologically to the retraction of the tongue root, and they don't relate to the tip or blade of the tongue.

Unfortunately, the named parts of the tongue do not correspond to intuition or common sense. When you look in the mirror your tongue looks kind of flat and thin. This is an illusion. Your tongue is really a big fat ball with a bit stuck on the front of it.

When we talk about the tongue, there is the front bit which we use for consonants. We can flap it about in all kinds of different ways. That's the blade of your tongue. It doesn't count for vowels in any way. The part of the tongue that we use for making vowels is the big ball of muscle behind that. It starts where the your tongue joins the floor or your mouth.

In the stylised diagram above, the blade of your tongue is represented by the small pink rectangular section. The square behind that represents the ball of your tongue. Now when we talk about "front" vowels and the "front" of your tongue raising, we are talking about the front of this back part of your tongue. So when you think of your tongue in normal everyday terms, this is actually about half way down your tongue as you look at it in the mirror. This is what raises towards the roof of your mouth when you make an [i] vowel. The blade of your tongue does nothing at all.

So the horizontal axis of a vowel quadrilateral shows whether it is the front of that bulky part of the tongue or the back of it that "is raising up". (The vertical axis represents the distance between the tongue and the roof of the mouth.)

That said, the production of vowels is much more complicated than the idealised and simplified descriptions relating to vowel labelling in terms of rounding, height and front/backness. And, especially with open vowels it is extraordinarily difficult, if it is possible at all, to finely manipulate the front or back vowel quality of the sound by consciously trying to change which bit of the tongue is most raised. It's far easier to hear examples of the sound and aim for those, or look at someone making an exaggerated articulation (preferably with no sound whatsoever) and try to produce the sound you think they are making. Another way is to produce the sounds down either edge of the vowel quadrilateral. So if aiming for [a], travel down the front vowels going from close to open. So go from [i] to [e] to [ɛ] and then continue lowering the jaw in the same way to [a].

Out of those different techniques, in my experience, by the far the most effective for non-high front or back vowels is the 'exaggerated' pronunciation. The best way of doing this is getting someone who can make the sound to pretend they are screaming the sound at the learner for a couple of seconds, but without making any noise at all. (Works beautifully.)

Answer 4

Peter Ladefoged, in A Course in Phonetics, quotes with apparent approval the words of another phonetician: “Phoneticians are thinking in terms of acoustic fact, and using physiological fantasy to express the idea.” This is the most succinct way I know to describe the ideas of vowel height and backness. Frontness and backness are acoustic ideas. They correspond to formant values, as the other answers indicate.

I worked in an ultrasound laboratory for a number of years, and then created a biomechanical model of the tongue for my dissertation. There is nothing in the tongue reducible to just two parameters. (Using a very technical approach, you can characterize whole vocal tract shapes using two gradient numbers, but those numbers do not correspond straightforwardly to tongue position.)

A more interesting question is how generations of students can be taught articulatory phonetics without ever raising the question you did!