MPiStutter is an app supporting Modifying Phonation Intervals (MPI) stuttering therapy. It analyzes the user's vocal fold activity and trains him or her to eliminate too-rapid speech elements and speak fluently at a normal speaking rate.

In a study of MPI stuttering therapy published in the Journal of Speech, Language, and Hearing Research, speech-language pathologists trained five adult stutterers to use MPI software running on a computer in a speech clinic. The stutterers then used the computer on their own, without SLP supervision. The subjects practiced 2-3 hours per day for 2-3 weeks. All five reached "near zero" stuttering on telephone calls to local businesses (a stressful speaking situation). Therapy was then discontinued. One year later all five subjects had maintained this fluency.

Because MPI stuttering therapy can be done on a computer without the presence of a speech-language pathologist, the therapy is uniquely suited to mobile devices such as the iPhone. MPiStutter moves stuttering therapy out of the speech clinic and into situations of daily living.

The screenshots show how MPiStutter measures the duration of phonation intervals. Phonation intervals are the periods of time your vocal folds vibrate to produce vowels and voiced consonants, delineated by voiceless consonants and pauses.

The first screenshot shows very short phonation intervals (under 100 milliseconds) color-coded red, orange, or yellow. These short phonation intervals indicate stuttering or too-rapid speech that precedes stuttering.

The second screenshot shows abnormally long phonation intervals color-coded blue or purple. These indicate fluent but abnormally slow speech, which characterize prolonged speech stuttering therapy (also known as fluency shaping or smooth speech).

The third screenshot shows fluent speech at a normal speaking rate. The green phonation intervals show the user that his or her vocal folds are moving neither too fast nor too slow. Note that normal speech contains a some shorter (red) and some longer (blue) phonation intervals. Normal speech constantly changes speed, volume, and prosody (emotional inflection). As long the user produces a large percentage of green phonation intervals he or she will speak fluently and sound normal.

MPiStutter also provides auditory feedback so that the user can have a conversation without looking at the screen. Short (red) phonation intervals switch on the user's voice in earphones, delayed a fraction of a second (delayed auditory feedback or DAF). DAF induces slow, fluent speech in stutterers. When the user is speaking fluently at a normal or slow speaking rate (indicated by green or blue phonation intervals) the DAF switches off. As the user improves vocal fold awareness and control and increasingly speaks fluently the DAF switches on less and less often. When the user can speak fluently without the DAF switching on he or she can discontinue using MPiStutter.

MPiStutter is ideal for stutterers who have learned to speak fluently in a speech clinic but are having difficulty transferring this fluency to conversations outside the speech clinic.