The most common sound that people substitute for /r/ is the /w/ sound. The /w/ sound is made with the lips and the /er/ sound is made with the tongue.
Tell the student to pull the back of the tongue to the back of the mouth. The edges of the tongue press up to the roof of the mouth and the tip of the tongue is raised up. Air goes over the tongue to say /er/. The mouth can be open about a finger's width. Do not close the teeth all the way. The tongue has to have room to go up and back.
If the student is saying “ah” the tongue is down and needs to go up. Sometimes the tongue is pulled back too far causing the back of the tongue to drop. It sounds like a distorted “ah” or like a choked "ah.” Instructing the student to bring the tongue forward just a bit more may correct it.
Sometimes it is easier for the student to start with their mouth open enough to say “ah” and then bring the jaw up enough to say “er.” The final production sounds like “ahr.”
Tell the student to pull the back of the tongue to the back of the mouth. The edges of the tongue press up to the roof of the mouth and the tip of the tongue is raised up. Air goes over the tongue to say /er/. The mouth can be open about a finger's width. Do not close the teeth all the way. The tongue has to have room to go up and back.
If the student is saying “ah” the tongue is down and needs to go up. Sometimes the tongue is pulled back too far causing the back of the tongue to drop. It sounds like a distorted “ah” or like a choked "ah.” Instructing the student to bring the tongue forward just a bit more may correct it.
Sometimes it is easier for the student to start with their mouth open enough to say “ah” and then bring the jaw up enough to say “er.” The final production sounds like “ahr.”