Device Monitor How to test your iPhone speaker and microphone
In Device Monitor, open Diagnostics > Audio. Run Speaker Test to hear tones from deep bass to high treble and listen for crackle, then tap Start Test under Microphone Test and talk - past 30% the app says Mic working!.
When you need a speaker and mic check
Usually it's one of three moments: someone on a call says you sound faint, music has started buzzing where it didn't before, or you're about to hand over cash for a used iPhone. A fixed-pitch tone beats music every time here, because a rattle or a distortion has nowhere to hide against a pure sound.
How to test iPhone 18 Pro speaker crackling
Since late September, owners of the iPhone 18 Pro and Pro Max have been describing the same thing: a faint crackle, tick or pop from the speaker, sometimes from the earpiece on calls. Some hear it all the time, others only when a notification lands, the keyboard opens or Airplane Mode is switched on and off. Apple has not said what causes it, and the first iOS 27 bug-fix update did not mention it.
So nobody can tell you yet whether your phone has a software glitch or a bad part. What you can do is write down exactly when the noise happens. That record is what makes a later comparison, or a visit to Apple, worth something.
- Take the case off and look at the bottom grille. Lint in there crackles too.
- Set the volume to about half and turn silent mode off.
- In Device Monitor open Diagnostics > Audio > Speaker Test.
- Play each tone in Frequency Sweep once: 250, 500, 1000, 2000, 4000 and 8000 Hz. Each lasts 3 seconds.
- Turn the volume to full and play 250 Hz and 500 Hz again. Low tones move the speaker the most.
- Write the result in the sheet below, one row per tone.
- Now try the triggers people report: switch Airplane Mode on and off, open the keyboard, drag brightness fast. Note which ones make the sound.
| Test | Volume | Output | Clean or crackle? | After the next iOS update |
|---|---|---|---|---|
| 250 Hz | Half, then full | Bottom speaker | ||
| 500 Hz | Half, then full | Bottom speaker | ||
| 1000 Hz | Half | Bottom speaker | ||
| 2000 Hz | Half | Bottom speaker | ||
| 4000 Hz | Half | Bottom speaker | ||
| 8000 Hz | Half | Bottom speaker | ||
| Voice note held to the ear | Half | Earpiece | ||
| Airplane Mode on and off | Any | Either |
Bottom speaker versus earpiece
The tones only play through the loudspeaker, in mono. The earpiece needs a different test: play a voice note or make a short call with the phone against your ear, in a quiet room. Several iPhone 18 Pro reports are about the earpiece on cellular calls, so test a cellular call and a Wi-Fi call if you can, and note which one crackles.
Compare before and after an iOS update
Keep the sheet. When the next iOS update arrives, run the same tones at the same volume and fill the last column. A noise that goes away with an update was software. A tone that still rattles at 250 Hz after the update points at the hardware.
Signs that point to service rather than software
- The same tone crackles every time, at the same volume, case off.
- It gets worse as the volume goes up, on low tones especially.
- It started after a drop or after the phone got wet.
- It still happens after a restart, with Bluetooth off and no other app open.
If two or more of those fit, contact Apple Support and show them the sheet. With a new phone still in its return window, that is a better use of your time than waiting for an update that may not come.
What Device Monitor cannot diagnose
It plays clean test tones and lets you hear the result. It does not record the speaker, measure distortion, read any hardware fault code or tell software from hardware on its own. Your ears and the sheet do the diagnosing; the app gives you a repeatable sound to do it with.
How to check if an iPhone speaker is damaged
- Pull the phone out of its case, kill silent mode, set volume to about half.
- Open Diagnostics > Audio - Speaker Test sits first.
- Tap Play Tone. You get a steady 3-second tone at whatever frequency is selected.
- Work through the Frequency Sweep list: 250 Hz, 500, 1000, 2000, 4000, 8000 Hz.
- Listen close to the bottom of the phone each time, then turn the volume up and go back through the low tones.
| You hear | Likely meaning |
|---|---|
| A clean tone at every step | The loudspeaker works across its range |
| Buzz or rattle on 250 Hz and 500 Hz only | A damaged or loose speaker membrane; low tones move it most |
| A tone that cuts in and out | A loose connection or damaged speaker |
| Silence on every tone | Check silent mode and volume first; if still silent, a speaker fault |
| Muffled sound that improves after cleaning the grille | Dust or lint, not a broken speaker |
One thing worth knowing before you panic: the tones are mono through the loudspeaker only. There's no separate left/right test and no earpiece test here, so to check the earpiece - the one you actually hold to your ear - make a short call or play a voice note with the phone up against it.
How to test the iPhone microphone
- Same Audio section, Microphone Test card sits right under the speaker one.
- Tap Start Test, allow mic access if it asks.
- Talk normally, about 20 cm from the bottom of the phone. The bar moves, the level shows as a percentage.
- Past 30% it says Mic working!. Tap Stop, and a pass reads Microphone is working correctly!.
That percentage comes from mapping the mic input onto a 60 dB window: dBFS loudness plus 60, divided by 60, clamped between 0 and 1, shown as a whole number. Silence sits near zero; shout and the bar fills.
| Mic input (dBFS) | Shown as | Status |
|---|---|---|
| -55 | Level: 8% | Speak into mic... |
| -45 | Level: 25% | Speak into mic... |
| -30 | Level: 50% | Mic working! |
| -20 | Level: 66% | Mic working! |
What the mic test cannot tell you
What this test won't tell you: it only reads the default microphone at the bottom. No way to pick front or back mics, and it never plays anything back, so it proves the mic picks up sound - not that it sounds clean. For actual quality, record a voice memo and listen, or make a real call.
Common mistakes
- Testing with the case still on - plenty of cases block the speaker or mic holes without you noticing.
- Blaming the speaker when it's silent mode or Bluetooth headphones taking the sound elsewhere.
- Covering the bottom mic with your own hand while holding the phone normally.
- Expecting the tones to shake water out of the speaker - there's no water-eject feature in this app.
Questions and answers
Is the iPhone 18 Pro speaker crackling hardware or software?
How do I tell if my iPhone speaker is blown?
Is there a left and right speaker test?
The mic test shows no level at all. Is my mic broken?
Can it measure how loud a sound is in decibels?
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