Some foreign speakers talk with very closed mouths. In English, we move our mouths a lot. This means that we open them. As one client stated, “you open your mouth REALLY WIDE!”
The short a and short o sounds are pronounced with a wide open mouth. When you do not, open your mouth wide enough, the short a and short o sound like short u. This makes a word sound different.
For example, bat (a) and bought (o) both become but.
To correct this mistake, just open your mouth more. It is opened in a wide circle for the short a. For the short o it is opened in a wide oval.
Try it…people with notice the difference!