By Grant Berry
Many will recall these vowels from English class in primary school, but what exactly is a vowel? What makes a vowel a vowel and not a consonant? As far as linguists are concerned, a vowel is any sound you make where the air from your lungs isn’t blocked in some way—like by your tongue, lips, or teeth—when you produce it. For example, if you make an s sound, your tongue raises and touches the front of the roof of your mouth, disrupting some of the sound coming from your lungs, but when you make an ah sound (like you’re at the dentist), this doesn’t happen. Even when you say ee (like in feet), which makes your tongue raise, the tip of your tongue doesn’t make contact with anything and the sound waves escape without too much resistance. Different varieties of English in the US vary widely in the number of vowels they use, but most varieties have at least twelve.
The range of variation in vowel systems across the US is a major defining feature of distinct varieties. Different regions of the US may change their pronunciation of certain vowels, making them sound different to people who aren’t from those areas. For example, you may hear a Philadelphian talk about the Iggles game when referring to Philadelphia’s football team, and you may hear someone from Pittsburgh say they’re going dahntahn when they’re heading downtown. It can also happen that the same word sounds different to people from different areas. In Philadelphia, the vowels in bought and bot sound different, but they’re the same in Pittsburgh (and most of the US, too). In Pittsburgh, steel and still sound the same, but not to speakers from most other regions of the US. In my hometown (Kansas City), pin and pen sound exactly the same, but I often confuse people here in State College (I also say melk instead of milk, which usually makes people I’m talking with cringe; sorry to gross you out, but that’s just my variety).
To measure variation in vowels, linguists first have to be able to properly locate them in your mouth. Where does your tongue have to be to make a specific vowel sound, and how can we tell from just listening to recordings? It turns out that the way that energy is filtered by your tongue when speaking tells us something about where the tongue is; the energy that’s not there is like the tongue’s acoustic shadow. Linguists use that information to extract focused areas of energy called formants (because together they form the whole speech signal). As it happens, the first two formants correspond pretty well to your tongue’s position in your mouth. The first formant tells us something about how high the tongue is, and the second formant tells us about how forward or backward it is. Together, this information allows us to get a pretty good guess where the tongue is when you make certain sounds, and we can then compare these data across speakers from different areas to see how they differ from one another.
Here are some of my vowels.
Like I said, I don’t pronounce pen and pin differently from one another, and I don’t make a distinction between caught and cot. My boot and feet vowels are also pretty fronted, which might be influence from my time doing research in Philly. In any case, you can see that vowels can be pretty variable, even when the same word is spoken by the same person—imagine how variable the categories are among speakers from different geographic areas, different age groups, and different language backgrounds! Where do you think your vowels are? Do pen and pin sound the same to you? What about cot and caught? How are your vowels different from your friends, your parents, or your teachers? The only way to know is to listen!