What does your tongue actually do when you speak?

New Scientist Magazine has an interesting article about how we can understand what our mouths do when we speak. I get annoyed quickly in trying to describe how my tongue presses my upper palate behind the teeth for the 'T' sound but further back for the 'D' sound. How far back? How hard do I press?

I am not sure if I will be better able to describe the positions and motions verbally but now those criteria can be measured.

In the past, sensor were placed in people's mouths but the sensors themselves altered the shape of the mouth. In a wonderful bit of creative thinking, the sensors have been placed in dentures of people missing their teeth, creating a natural topography for people to speak inside.

From the article:

'Neat trick'

With the physiology of the mouth largely unchanged, the patients could speak normally while the measurements were being taken. They were asked to recite tongue twisters – phrases that are designed to be difficult to articulate rapidly – to generate the results.

"This is a neat trick; a new twist on a methodology that has been around for some time. The idea of using denture patients in this way is clever," says Joe Perkell, a researcher in MIT's Speech Communication Group in Cambridge, Massachusetts, US.

The researchers have so far published results on the production of the sound "T", and are now turning their attention to other vocalisations. "We could use up to five sensors at the same time in this device," says team member Christophe Jeannin, adding that they also plan to recruit more volunteers for the forthcoming work.