A diphthong is two vowel sounds together. That means your mouth has to move: there is a beginning and an ending position. Study this diphthong with illustrations and up close, slow motion speech.
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The ‘ay’ as in ‘say’ diphthong. The first sound in this diphthong does not occur on its own as a vowel in American English, e, e, ay. To make this first sound, the tongue will push forward and press behind the bottom front teeth, e, e. The front part will be wide, ay, ay. The second half is the ‘ih’ as in ‘sit’ vowel. So to make this part of the diphthong, the front/mid part of the tongue will raise towards the roof of the mouth, ay, ay. As the tongue raises, the jaw will close somewhat. Ay, say.
Here are the two sounds side by side. You can see that in the first sound of the diphthong, the jaw is dropped slightly more. Here are the two sounds in profile. Again, note that the jaw drops slightly more for the first sound. Here, parts of the mouth are drawn in. In the first sound of the diphthong, the tongue pulls more forward. In the second sound it is more forward and up, and the tongue raises closer to the roof of the mouth. In both sounds, the tip of the tongue is touching the front bottom teeth. Sample words: maybe, play, neighbor. Sample sentence: I was afraid if I stayed late that I’d be tired today. Now you’ll see this sentence up close and in slow motion, both straight on and from an angle, so you can really study how the mouth moves when making this sound.
I, with the ‘ai’ as in ‘buy’ diphthong, was, lips make the W shape, afraid, bottom lip up for the F, and now here is the ‘ay’ as in ‘say’ diphthong. Tongue tip up to make the D. If I stayed, again the ‘ay’ as in ‘say’ diphthong, and the tongue tip up for the D. Late, again the ‘ay’ as in ‘say’ diphthong, and the tongue moves into the T position. That I’d be tired, with the ‘ai’ as in ‘buy’ diphthong, today. Again the ‘ay’ as in ‘say’ diphthong.
And now from an angle. I, with the ‘ay’ as in ‘buy’ diphthong, was afraid. The ‘ay’ as in ‘say’, tongue forward and then up more towards the roof of the mouth. There the tip makes the D. If I stayed, again the ‘ay’ as in ‘say’ but it’s very quick here, the jaw doesn’t drop much before the tongue moves up to make the D sound. Now here’s the L, and it pulls down again, la-, into the ‘ay’ as in ‘say’ diphthong. That I’d be tired today. And again, the ‘ay’ as in ‘say’ diphthong. The jaw drops, the tongue comes forward, and then the jaw closes as the tongue raises towards the roof of the mouth. That’s it, and thanks so much for using Rachel’s English.