PROVO — When people make the sounds f, v or th, others can see their tongues moving at the front of the mouths.

By when they make vowel sounds, it's more difficult to see how and where the tongue hits the palate.

Placement of the tongue is crucial in learning how to speak. And a person who is deaf or suffers from a stroke or speech impediment must train the tongue about placement against the palate.

Thomas Fletcher has spent more than 30 years in an almost five-decade career developing the palatometer — a device that measures where the tongue hits the palate — and he believes it can help deaf people, stroke patients and people with speech impediments learn to speak more clearly.

The device has three components: a mouth piece speckled with 118 tiny gold sensors that resembles an orthodontic retainer, an interface worn around the neck that connects to a computer, and computer software that shows a simulated tongue enabling patients to see where their tongue is hitting the palate in real time.

"Getting the tongue in the right place is so hard if you're deaf or had a stroke," said Fletcher, who is semiretired and does research part time for Brigham Young University's audiology and speech-language pathology department. "Once it feels right (inside the mouth), it'll sound right."

"Now we're really giving them a visual sign," said Christopher Dromey, a professor in the department at BYU who has conducted research with Fletcher.

The palatometer is used during speech therapy. Both the speech-language pathologist and person learning to speak place a "pseudo-palate" piece inside their mouths and wear the interfaces to practice speaking.

The computer software shows pictures of two simulated mouths.

As the speech therapist pronounces a sound, the tongue touches specific sensors — for instance, when making the s sound, the tongue touches sensors in the front of the mouth near the upper front teeth; the sh sound is a little farther back in the mouth, and the b and p sounds are made when the lips smack together.

When tongue or lips touch the sensors, blue dots light up on the simulated mouth that correspond to the sensors in the speech-language pathologist's mouth.

After the speech-language pathologist pronounces the sound, the person learning to speak tries to imitate, positioning and repositioning the tongue and lips using the simulated mouth as a guide.