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Will Styler

Associate Teaching Professor of Linguistics at UC San Diego

Director of UCSD's Computational Social Science Program

Theta and Eth: Your New Phonetic Friends

This was originally posted on my blog, Notes from a Linguistic Mystic in 2007. See all posts

I’m a big phan of phonetics (OK, I’ll stop now). Phonetics is the study of speech sounds, and how we make and hear them. One of the very first tasks when studying phonetics is to listen very closely to your native language, and start hearing the sounds that we ignore, can’t hear, or just never think twice about in our native language. This process can be really interesting, seeing the world of complexity in speech that we never quite notice in our everyday lives. To share a bit of this, I’m going to talk a little bit about two English distinctly different sounds that are usually considered to be one sound by Native Speakers: Theta and Eth

A Primer on Voicing

Before we discuss our new phriends, we have to talk a little about how we make some consonants. I’ve discussed the idea of “voicing” before, in my post “Unaspirated T’s from the mouths of Babes”, but I think it might be helpful to review the idea and rephrase a little bit. In the above post, I recommended that readers do the following quick experiment to get a sense of what voicing means. Give it a try again, if you’d like:

Put your fingers on your neck (guys, find your adam’s apple) and say “Ahhhhhhhh”. You’ll feel a vibration. That’s your vocal folds vibrating to give the A its sound. Now, keep your fingers there and say “Dadadadadadadada”. You’ll feel your tongue moving, but the vibration will be pretty constant. Now, try “Tatatatatatatata”. This time, the vibrations will feel like they’re going on an off, off during the T, on during the A. This is because, as I said above, T is a “Voiceless” sound, and D is “voiced”. (If you’re still interested, try the same with “Kakaka” and “Gagaga”, as well as “papapa” and “bababa”).

“Voicing” in phonetics, is just a fancy word for when the vocal folds (a more accurate term for the “vocal cords”) are brought close together, so that when air blows between them, they produce a vibration, and thus, a sound. It’s just like if you press your lips together and blow out your mouth, your lips vibrate (slowly), and produce an (altogether different) sound. For videos and pictures of this (which is taken by a camera inside somebody’s throat, so maybe not for the squeamish), check out this site.

Just like in the above experiment, whether or not the vocal folds are vibrating while your mouth and tongue make the required gestures can be the only difference between two consonant sounds (sounds created by obstructing the airway, unlike vowels). That’s the only difference between “Ta” and “Da”, between “Ka” and “Ga”, and between “Pa” and “Ba”. So, keep this contrast of “voiced” versus “voiceless” sounds in mind as you read on.

A tale of two TH’s

Say “This thistle” a few times. Now, pay very close attention to the TH sounds at the beginning of each word. Put your hand on your Adam’s Apple (or equivalent area on your neck) while you say them. After a few tries, you’ll notice that, in the words of a friend of mine, the “TH” in “This” is “more buzzy”, or, put more scientifically, voiced. This sound, the TH in “This, That, The, There, Then, Those…”, is called an Eth (pronounced with a voiced, Eth sound). In the International Phonetic Alphabet (IPA), it has this symbol:

The TH in “thistle”, or “theater, theory, think, thought, throw, through…” is called a Theta, and is Eth’s voiceless counterpart (Theta is to Eth as T is to D). Theta’s IPA symbol is, shockingly, a theta, as shown here:

Aside from voicing, there is no difference between them. The sounds are produced with the tongue in the same position, the tongue is doing the same thing for both, and all the other various phonetic phactors (I couldn’t resist) are the same. The only difference between the the Theta and the Eth is vocal fold vibration, but what a difference it makes.

Your writing system is lying to you

Now that you’re listening for it, there’s (eth) a big difference between the two sounds, but chances are, you never gave them a second thought (theta). Personally, I blame the English writing system. Writing systems complicate our lives when we’re learning phonetics, and in fact, the English writing system is the main reason that most English speakers don’t know that there’s a difference between Theta and Eth.

“This” and “Thistle” are spelled with the same TH, and there’s never a situation where the two sounds are used in identical contexts (When you see a TH in a word, it’s always clearly one or the other). In fact, say this made-up word, “thaxis”. I’ll bet you made a “theta”, if you’re a native English speaker. We never read unfamiliar TH words with Eth, and new words with Eth are few and far between.

So, in our everyday life, there’s not much need to know the difference between these sounds. Between our writing system and the system of English Phonology (where and when sounds are used), we’re seldom given a contrast between the two.

So, Theta, Eth, meet your new friend. You’ll never look at “TH” the same way again. You don’t have to thank me when you catch yourself sitting at the dinner table, endlessly repeating a word to figure out if it’s Eth or Theta. Phonetics addiction is Phun, isn’t it?