English Pronunciation 18: The /ɔɪ/ sound

The /ɔɪ/ sound has two single vowel sounds joined together to make
the one sound.

To make the /ɔɪ/ sound, you start with the single
/ɔ:/ sound and the single /ɪ/ sound. You move from the /ɔ:/ sound
to the /ɪ/ sound ‒ your voice glides from the first (1st) to the second
(2nd) sound.

You say and hold the first sound /ɔ:/ and then say the
second sound /ɪ/ quickly, as a short sound. When you say the /ɔɪ/
sound, you want to say about 60% of the /ɔ:/ sound and about 40%
of the /ɪ/ sound. You need to make sure that you do arrive at (say)
the second sound, /ɪ/.

So, what we do when we make this sound is,
we take the /ɔ:/ sound and put it together with the /ɪ/ and end up
saying a new sound, /ɔɪ/.