PowerDAF: Delayed Feedback

PowerDAF is a speech practice app for people who stutter. At its heart is delayed auditory feedback (DAF): you speak into the microphone and hear your own voice in your headphones a fraction of a second later. DAF has been studied for decades, and its effect varies from person to person: some people find speaking easier with it, others don't. PowerDAF lets you try it and find the settings that suit you. It complements work with a speech therapist; it doesn't replace it.

SPEECH
• Live DAF, with a delay from 0 to 300 ms
• Frequency-altered feedback (FAF): shift your voice up or down by up to 12 semitones
• Masking noise (MAF) that comes in while you speak and fades in the pauses, including a masking-only mode
• 6 built-in presets, plus your own
• The real delay at your ear: what you set, plus the latency of your headphones and iPhone
• Find your delay: three short rounds of comparing two delays by ear
• Keeps running when you lock the screen

BEFORE TALKING
A 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 or microphone needed.

PRACTICE
• 10 techniques with step-by-step sessions: easy onset, prolonged speech, light contact, speaking on the exhale, pausing and phrasing, pull-out, cancellation, preparatory set, voluntary stuttering, desensitisation
• Speech rhythm: a metronome from 30 to 160 BPM, with sound, vibration or on-screen beats only
• Reading aloud: 27 passages in each language, from sounds and tongue-twisters to longer texts and unscripted speech, with a phrase-by-phrase pacing guide
• Record yourself and listen back, if you want to
• Into everyday life: plan one real situation, then note how it went
• An avoidance diary and a situation ladder

CALM
Five breathing patterns, speech-muscle relaxation, 5-4-3-2-1 grounding and working through a block.

PROGRESS
Minutes practised, practice days, a 14-day chart, how speaking felt, and your tension before and after. No fluency percentages and no counting of stutters. Export your log as a JSON file, for yourself or to show your speech therapist.

PRO — A ONE-TIME PURCHASE
• Situation rehearsals: 11 conversations with the other person's lines, branches and a plan for blocking — ordering at a counter or by phone, calling a clinic, a job interview, answering in class, a voice message and more. “Introducing yourself” is open to everyone.
• Your own situations: write the lines for a conversation you have coming up, and the app adds the warm-up, the plan for blocking and the debrief
• A four-week programme: 20 steps through the app's exercises, each with a short note, at your own pace and with no schedule. Week 1 is open to everyone.
• Texts for work and study: six passages in each language — introducing yourself to a team, a work call, a meeting update, answering in class, opening a talk, “tell me about yourself”
• Your own words: paste what you actually need to say and rehearse it syllable by syllable or read it aloud with the pacing guide
Everything else is free, with no time limit. There is no subscription. What you write yourself stays yours, even if you refund the purchase.

HEADPHONES
Live DAF needs headphones, and wired ones work best: Bluetooth adds a delay of its own. Breathing, rhythm, exercises and reading work without headphones. Keep the volume moderate.

PRIVACY
No account, no ads, no analytics. Audio is processed on your iPhone and is not sent anywhere. Recording starts only when you tap record; only your latest take is kept, and it is deleted the next time you open the app.

8 languages: English, Russian, German, French, Spanish, Italian, Portuguese and Arabic. Drill words, tongue-twisters and metronome lines are written for each language, not translated. You can switch the language inside the app.

PowerDAF is not a medical device and does not diagnose anything. If stuttering started suddenly in adulthood, please see a doctor.