There are two vowel sounds that are similar to Long-vowels because they have two parts. However, these two vowels do not have an alphabet letter to represent them, so I use the IPA (International Phonetic Alphabet) symbols for these two sounds. They are:
Vowel /aw/
This is the sound in words such as: house / out / now / flower. This sound is usually spelled with the letters “OU” or “OW”, BUT be careful…
- not every word with “OU” has this sound. The vowel pair “OU” has many different pronunciations (this is explained in OU – Oh no!).
- not every word with “OW” has this sound. Some words with “OW” have a Long-O sound, such as “slow” or “own”.
Vowel /oy/
This sound is in words such as: boy / oyster / oil / choice. This vowel is spelled with either “OI” or “OY”.
These two vowels are not usually difficult for students to pronounce. In fact, I have never seen a situation where someone has had difficulty communicating clearly in English due to errors with these two vowels.
There is just one thing to keep in mind about pronouncing them. Since these vowels — as well as the regular Long-vowels — have two parts, the tongue needs to be active. So, to pronounce them well, the tongue needs to move or slide, in order to pronounce both parts, and to sound clear and natural.
PronunciationCoach 
Why do you say this /aw/ is the sound in house and flower? Why do you not note it /ow/? To me, aw would be making the sound as in awe or awful or aught.
This is precisely the most tricky part of trying to put labels on English vowel sounds. When a symbol is between slashes, that is the format for IPA symbols, so /aw/ is the IPA sound. Using “OU” or “OW” runs into problems because words spelled with “OU” have 8 different vowel sounds, and words spelled with “OW” use both Long-O and /aw/. It is a very complicated situation! Here are some of my recent posts on these topics: