How the HearAge amplifier works
HearAge picks sound up with the iPhone microphone, reshapes it across nine frequency bands, and plays it into your headphones a fraction of a second later. This page walks through that path stage by stage, and through the controls you get over each part of it.
The signal path
- The microphone. Capture happens on the iPhone itself, so the phone is the thing you aim. Point the back of it at the television, the lectern, or whoever is talking.
- A nine-band equaliser. Every band carries its own gain: 250, 500, 1,000, 1,500, 2,000, 3,000, 4,000, 6,000 and 8,000 Hz. The spacing tightens between 1.5 and 6 kHz because that is where consonants sit, and plain octave spacing would leave holes right through them.
- A compressor. Loud moments get pulled down as they arrive, which is what lets the quiet sound you came for come up without a door slam arriving at the same level.
- A limiter. A brick wall in front of the output. The compressor takes a couple of milliseconds to react, so anything sharp enough to slip past it gets stopped here.
- Your headphones. The app won't start without them.
Why headphones are required
Headphones keep the amplified output away from the microphone that is picking the sound up. Through the phone speaker, the microphone would hear its own output and the whole loop would squeal. Wired sets and AirPods both work.
The presets, and what each one changes
Four of them, and each is a gentle tilt rather than a wholesale rebuild of the sound:
| Preset | What it does to the shape |
|---|---|
| Conversation | Lifts 1–4 kHz a little, where most of a voice's detail lives |
| TV | Lifts 500 Hz–2 kHz, the band a television speaker throws across a room |
| Restaurant | Lifts above 2 kHz and pulls down below 500 Hz, where a busy room rumbles |
| Lecture | Lifts everything above 1 kHz for a voice you are sitting a long way from |
Each preset is defined on six octave points from 250 Hz to 8 kHz, then interpolated onto the nine bands the audio engine actually runs.
The boost slider
Boost is held separate from shape, so pushing it up never distorts the tilt your preset gave you. The app splits it across the compressor: part of it goes in before, the remainder is added afterwards as makeup gain with the limiter guarding the ceiling. Sealed earbuds passively block a good deal of the room, which is why the range goes as far as it does. Super Boost adds another 8 dB for a source that is genuinely distant.
Manual mode
Manual mode hands you the nine bands directly, one slider each, up to 18 dB apiece. Touch any of them and the preset stops applying. The chart above the sliders shows what each band is currently getting, so the shape you have built stays visible while you build it.
Noise suppression
Switching this on turns up a downward expander sitting below the level of whatever you are listening to. Sound underneath that floor gets pushed further down, so a room's steady hiss stops climbing alongside everything else. The threshold tracks the room as it changes, riding just under the sound you actually want.
What it's for
A television you would rather not turn up. A lecture or a tour guide you are sitting too far back from. Table conversation that a noisy room keeps swallowing. Birdsong, and other faint things worth listening in on.
HearAge is a listening tool for situations like those. It does not measure your hearing, and every setting in it is one you chose.
Listening safely
Amplified sound through headphones can get loud. Start low and bring it up gradually, and stop if anything is uncomfortable. The limiter holds a ceiling, though it has no way of knowing what level is right for your ears. Don't use the amplifier where you need to hear traffic or warnings.
Privacy, by architecture
Microphone audio is processed live and never recorded, saved, or transmitted. Your presets and manual settings stay on the iPhone. There is no account and no server. Details in the privacy policy.
Not a medical device. HearAge is a listening tool for everyday situations. It is not a hearing aid, and it does not diagnose, treat, or compensate for any medical condition. If you have concerns about your hearing, or notice sudden changes, pain or ringing in one ear, see a qualified professional.
Try it with the headphones you already own. Free, with no ads and no account.
Get HearAge for iPhoneFrequently asked questions
Why does HearAge need headphones?
They keep the amplified output away from the microphone picking the sound up. Through the phone speaker the microphone hears itself, and that is what makes a system squeal. Wired headphones and AirPods both work.
How much delay is there?
A fraction of a second. Capture, shaping and playback all happen in one short audio path, so it arrives closely enough behind the room that watching someone speak still lines up.
Is HearAge a hearing aid?
No. It's a listening tool for everyday situations, not a medical device and not a hearing aid, and it does not diagnose, treat, or compensate for any medical condition.