MPiStutter iOS app — $99.99

MPiStutter is temporarily unavailable while we make software updates.

Apple will remove MPiStutter from the App Store soon as we can’t afford to update the app for the new iPhones. After that we won’t be able to support you if your app doesn’t work, you lose your phone, etc.

MPiStutter supports 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 to speak fluently at a normal speaking rate.

MPiStutter requires training with a speech-language pathologist, but after that MPiStutter can be used without the presence of a speech-language pathologist. The app is uniquely suited to parents doing therapy practice with their child at home, or adults practicing speech therapy outside of the speech clinic.

What Is MPiStutter?

The following 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. A phonation interval 37 milliseconds long is shown below.

A phonation interval.

A phonation interval (37 ms duration)

The first screenshot (below) shows 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.

Red intervals

Short red intervals indicate stuttering or rapid speech

The second screenshot (below) shows 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).

Blue intervals

Long blue intervals indicate abnormally slow speech

The third screenshot (below) 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.

Green intervals

Green intervals indicate normal, fluent speech

MPI stuttering therapy can be done using only visual feedback (without earphones). But MPiStutter also provides auditory feedback so that the user can have a conversation without looking at the screen. Short (red) phonation intervals switch on delayed auditory feedback (DAF) to induce 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.

The main window (screenshots above) shows the last four seconds of the user’s speech. Above this a bar graph displays the last ten minutes of the user’s speech. The goal is to make the green bars tall and the red, orange, and yellow bars short.

The Cumulative screen displays the total talk time for the day, percentage too-short intervals, and a bar graph displays daily totals for each duration of phonation intervals. The goal is to get 2-3 hours of talk time per day, while each day reducing the percentage of short intervals.

Cumulative screen

Cumulative screen

The Evaluation screen is used to evaluate the user’s speech. The user reads a story and the app measures syllables per second and percentage too-short phonation intervals. The goal is to talk at a normal speaking rate with few short intervals.

Evaluation screen

Evaluation screen

MPI Compared To Fluency Shaping

Prolonged speech, also known as fluency shaping, increases phonation durations. The result is slow, abnormal-sounding speech. Fluency shaping therapy typically starts at 5-10 times slower than normal speech, then progresses to 2-3 times slower than normal speech, and ends at a “slow-normal” speaking rate that is somewhat slower than normal speech but sounds acceptable to listeners.

We recommend MPiStutter only for stutterers who have completed a fluency shaping therapy program. We view MPI as the next step, in which fluency is developed at normal speaking rates.

MPI Compared To Altered Auditory Feedback (AAF)

MPI and AAF treat different aspects of stuttering. The two treatments are complimentary, not competing. One is not better than the other.

Several neurological abnormalities are associated with stuttering, suggesting that several factors contribute to stuttering, and that treatments that address only a single factor will never be 100% effective. The neurological abnormalities most often associated with stuttering are underactive auditory processing and overactive speech motor processing.

Altered auditory feedback (AAF) changes how to user hears his voice. The most common forms are delayed auditory feedback (DAF) and frequency-altered auditory feedback (FAF). AAF stimulates auditory processing and typically reduces stuttering about 70% at a normal speaking rate. The effect is immediate, requires no training or mental effort, and sounds normal. Two studies found that the School DAF device produces about 50% long-term carryover; however, other studies have found that SpeechEasy DAF devices don’t result in carryover fluency.

DAF can also be used to slow speech by increasing phonation durations. This treats the overactive speech motor processing associated with stuttering. The result can be close to 100% fluency but with slow, abnormal-sounding speech.

MPI therapy treats only the overactive speech motor processing associated with stuttering. The results are seen after practicing typically several hours each day for weeks or months. Additionally, some stutterers don’t respond to MPI therapy. These stutterers may have a more severe auditory processing disorder and need AAF treatment.

MPiStutter provides both MPI and DAF so that users can speak fluently immediately, and over time need the DAF less and less. As the user produces fewer short phonated intervals the DAF switches on less often. The result is “the best of both worlds,” or immediate and long-term fluency.


MPiStutter runs on Apple’s iPhone, iPod touch, and iPad. MPiStutter can’t be used on telephone calls on the iPhone.

MPiStutter requires wearing a throat microphone to accurately monitor vocal fold activity. You can use MPiStutter with Apple’s earphones and microphone (MB770G) if you tape the microphone against your throat using medical tape.

Apple earphones and microphone

Apple earphones and microphone

Another option is the Iasus NT3 throat microphone. This throat microphone rejects background noise well and is popular with military personnel, law enforcement, and paintball enthusiasts (i.e., it looks cool).

Iasus NT3 throat microphone

Iasus NT3 throat microphone

The Iasus NT3 includes a monaural (one ear) earphone. The microphone can be hidden under a shirt with a collar. The earphone is the type used by television announcers; it’s invisible to listeners in front of you.

How To Buy MPiStutter

Buy MPiStutter from Apple’s App Store. Schools get the app for half-price with their educational discount.

Available on the App Store


MPiStutter instructions are on their own webpage.

Webpage last updated: July 23, 2014

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