Delayed-feedback speech practice for stuttering
PowerDAF is a speech practice app for people who stutter. Speak into your iPhone and hear your own voice in your headphones a fraction of a second later — delayed auditory feedback, or DAF. Around it sit speech techniques, breathing, reading aloud and a minute to get ready before you talk. It complements work with a speech therapist; it does not replace it.
When you hear yourself back with a small delay, many people who stutter find that their speech flows more smoothly while the delay is on. It does not help everyone, the effect usually lasts only while DAF is on, it differs a lot from person to person, and for some it fades with time — so PowerDAF lets you try it and find the settings that suit you.
Live DAF needs headphones, and wired ones work best — Bluetooth adds a delay of its own, and the app tells you so. Through the iPhone speaker the microphone would pick its own sound back up, so the app will not start a session there.
You hear your voice 50 ms later to begin with, adjustable from 0 to 300 ms, with optional pitch shift and masking noise. The session keeps running with the screen locked, and the app shows an estimate of the real delay at your ear.
Compare two delays by ear over a few short rounds, save the settings you like as presets, and afterwards note how speaking felt. That goes into a practice log — never a score.
Delay from 0 to 300 ms, frequency-altered feedback that moves your voice up or down by as much as 12 semitones, and masking noise — including a masking-only mode. Six built-in presets, plus your own.
No account, no ads, no analytics, no tracking and no third-party code. Live audio is processed in memory and never saved, a recording starts only when you tap record, and the app sends none of your data anywhere — it leaves the phone only in an export you make yourself, or in your own iPhone backup if you use one. The only connection the app makes is to Apple’s App Store, for the Pro purchase.
Step-by-step sessions for easy onset, prolonged speech, light contact, speaking on the exhale, pausing and phrasing, pull-out, cancellation, preparatory set, voluntary stuttering and desensitisation.
27 passages in each language, from single sounds and tongue-twisters to longer texts and unscripted speech, with a phrase-by-phrase pacing guide. A speech-rhythm metronome runs from 30 to 160 beats a minute.
One minute to get ready for a call, an order, meeting someone, speaking to a group or a hard conversation: breathing, releasing tension, the first word, the first phrase. No headphones needed.
Plan one real situation, then note afterwards how it went. An avoidance diary and a situation ladder help you choose the next step at your own pace.
Five breathing patterns, speech-muscle relaxation and 5-4-3-2-1 grounding. All free, and none of it needs headphones.
Minutes practised, practice days, a 14-day chart and how speaking felt. PowerDAF never counts stutters and gives no fluency score. Export the log as a JSON file to show your speech therapist.
PowerDAF does not diagnose or treat anything, and it is not a cure for stuttering. It is a place to practise.
DAF makes speaking easier for some people and not for others. Where it helps, the effect usually lasts while it is on, and for some people it fades over time.
It is meant to be used alongside a speech-language therapist: they choose the technique, and you rehearse it here. If stuttering began suddenly in adulthood, see a doctor first.
Only live DAF needs them. Breathing, the metronome, the techniques, reading aloud and “Before talking” all work through the speaker or in silence.
The app limits its own output, but your iPhone’s volume still decides how loud it is. Your voice should sound a little louder than usual, no more — and 10 to 20 minutes at a time is plenty.
English, Russian, German, French, Spanish, Italian, Portuguese (Brazil) and Arabic, right to left. Reading passages and metronome lines are written for each language, not translated, and the text follows your Dynamic Type setting, including the larger accessibility sizes.
No trial, no time limit, no daily cap. One optional purchase adds practice material; it does not make the free part any smaller.
Live DAF, pitch shift and masking over their full range, all six presets and your own, all ten techniques, the whole reading library, “Before talking”, breathing, relaxation and grounding, the metronome, “Into real life”, the avoidance diary, the progress log and its export.
Your own texts: paste what you actually have to say and practise it syllable by syllable with the metronome, or phrase by phrase with the pacing guide. Plus situation rehearsals with the other person’s lines — “Introducing yourself” is open to everyone. A one-time in-app purchase through Apple, shareable with Family Sharing. There is no subscription.
The full documents that apply to the PowerDAF iOS app. Plain language, no surprises.
What we collect (nothing), what the microphone is used for, what stays on your iPhone and how to delete it, and how Apple’s own reporting works.
Read the policyYour licence to use the app, why it is not medical advice, safe use with headphones, the one-time purchase, and the usual legal limits.
Read the termsSend us your iPhone model, iOS version, the headphones you use and a short description. You do not need to tell us anything about your speech. We reply to every message.