Your phone has several microphones, and that is the key to diagnosis
Modern Android phones carry two or three microphones: a main mic at the bottom for calls and recordings, a top mic near the earpiece or rear camera for noise cancellation and speakerphone, and sometimes a third for video and stereo capture. Different features use different mics, which is why the failures are so specific: your voice can be fine in a normal call but vanish on speakerphone, or clear in a voice memo but silent to the assistant. This multi-mic reality is the single most useful fact for diagnosis, because WHICH situations fail points at WHICH mic.
Start every microphone investigation with the objective test that settles the biggest question, is the main mic working at all? Our Microphone Test shows a live waveform from the primary mic; speak, and a jumping waveform proves the main mic and the phone's audio input path are healthy, which immediately narrows the problem to a specific app, a specific feature, or a secondary mic. A flat line with permission granted points toward the main mic itself or a system fault. Thirty seconds here saves you from misdiagnosing an app problem as a broken mic and vice versa.
Map your specific failure against the mics before fixing. Nobody hears you in ANY app: main mic or system, and the app-and-permission plus cleaning fixes below apply broadly. Fine normally but silent on speakerphone or in videos: the top or secondary mic. Fine in recordings but not in one particular app (WhatsApp calls, a specific game): that app's permission or bug. Fine to the phone but robotic or faint to the OTHER person on calls: often noise-cancellation or network, not a dead mic at all. Naming the pattern is ninety percent of the fix.
Permissions, connections and the app-level fixes
The most common 'broken microphone' is a permission the app never received. Android gates mic access per app, and a denied or reset permission produces total silence from that app while every other app works. Settings, Apps, the affected app, Permissions, Microphone, set to Allow. Sweep the apps that matter, phone, messaging, video-call and assistant apps, since a system update or a privacy cleanup can reset these. Also check the global privacy toggle some Android versions add: a 'Microphone access' master switch in privacy settings, or a quick-settings mic-off tile, silences every mic system-wide when off, and an accidental tap explains a sudden total failure.
Rule out the audio being routed elsewhere, because a phone sending mic duty to a Bluetooth device is not a broken mic. Connected earbuds or a car use THEIR microphone for calls, and a dirty or distant earbud mic makes you inaudible while the phone's own mic is fine, disconnect Bluetooth and retest on the phone directly. The same applies to a plugged-in headset with an inline mic. This single check resolves a surprising share of 'my mic broke' reports, especially the ones that started when new earbuds arrived.
For a failure confined to one app, treat the app, not the phone. Clear the app's cache and data (Settings, Apps, the app, Storage), update it, or reinstall it; app-specific mic bugs are common and usually fixed in the app's own next version. If the assistant specifically cannot hear you, check its own settings (Voice Match, hands-free access) plus the mic permission. And restart the phone before deep fixes, a stuck audio service is a real and common cause of sudden mic silence, and the reboot clears it in the time it takes to power-cycle.
Physical causes: the blocked or dirty mic
Microphones speak to the world through tiny holes, and those holes clog. The main mic is a pinhole at the bottom edge near the charging port; the secondary is near the top or the rear camera. Pocket lint, dust and grime pack into them over months, muffling or silencing your voice gradually enough that you blame everything else first. Clean gently: a soft dry brush (a clean toothbrush) worked over the hole, or a burst of compressed air held at a distance. Never jam a pin deep into a mic hole, the membrane behind it is delicate, and puncturing it converts a dirty mic into a dead one.
Cases, protectors and covers are the accidental blockers. A case whose cutout does not align with the mic hole, a screen protector overlapping the top mic, or a stick-on wallet covering the bottom edge can muffle you convincingly, especially cases installed slightly off. Remove the case and test; if your voice returns, reseat or replace the case. This is a five-second check that resolves a real fraction of 'muffled on calls' complaints, particularly right after a new case.
Water and moisture are the acute physical cause. A phone that got wet can have water sitting in the mic cavity, muffling or killing input until it dries; our water-damage guide's drying protocol applies, and the Speaker Cleaner's tone can help evict droplets from adjacent openings. Give a wet phone days, not minutes, before concluding the mic is dead. And after any physical cleaning or drying, re-run our Microphone Test to confirm the recovery objectively rather than guessing from a single phone call, the waveform tells you immediately whether the input is back.
The tricky case: they can't hear you, but your mic works
A frequent and confusing scenario: our Microphone Test shows a perfect waveform, recordings play back fine, yet people on calls say you are faint, muffled, cutting out or robotic. This usually is NOT a broken mic, it is call audio, and the causes live elsewhere. Noise cancellation gone wrong is a classic: the secondary mic that suppresses background noise can, if blocked or faulty, suppress YOUR voice instead, so a phone that sounds fine in recordings (main mic only) but poor on calls (both mics working together) points at the secondary mic or its blockage, clean the top mic hole specifically.
Network and codec factors impersonate mic problems on calls. A weak signal makes calls break up and sound robotic in both directions, and the fix is our no-signal guide (Wi-Fi calling, VoLTE, coverage), not the microphone. VoIP calls (WhatsApp, Messenger, Meet) degrade with poor internet, test on a strong Wi-Fi connection before blaming hardware. And the other person's phone, earpiece or connection can be the actual fault, if you sound bad to one caller but fine to another, the variable is not your mic.
Isolate methodically: record yourself with our Microphone Test and a voice recorder (proves the main mic), make a normal call and a speakerphone call (compares main versus secondary mic), and make a VoIP call on strong Wi-Fi (removes cellular from the equation). The pattern names the culprit, main mic fine plus speakerphone bad equals secondary mic; everything fine except cellular calls equals network; bad everywhere including recordings equals main mic or system. This mapping is the difference between cleaning the right hole and fruitlessly resetting a phone whose mic was never the problem.
The hardware verdict, repair, and prevention
The microphone earns a hardware conviction when our Microphone Test shows a flat line despite granted permission, no Bluetooth routing, a clean hole and a restart, or when a specific mic fails consistently (silent recordings, or inaudible speakerphone) after cleaning and a factory reset (backup first, per our reset guide) rules out software. Mics fail from water corrosion, drop damage to the mic or its flex connector, and simple age. The failure often accompanies a story, a swim, a drop, and that history plus the objective flat-line test is a solid diagnosis to bring to a shop.
Repair is among the friendlier ones: microphones are small, inexpensive components, and replacing one (or reseating its connector after a drop, worth requesting first, as in every repair chapter) is a modest job at most repair shops. On many phones the bottom mic shares a flex assembly with the charging port, so a phone with both a dead mic AND charging trouble may need one part that fixes both. Quote the specific mic, test at the counter with our Microphone Test and a call, and document the before-and-after with our report generator if the phone is headed for sale.
Prevention is unglamorous and effective: keep the mic holes clean (a monthly brush during your general phone cleaning), choose cases with properly aligned cutouts and seat them correctly, and keep the phone dry, water is the leading mic killer. Run our Microphone Test occasionally, ten seconds, especially before an important call or interview, so a dying mic surprises you at your convenience rather than mid-meeting. A cared-for mic outlives the phone, and when a call sounds bad, the test instantly tells you whether to clean a hole, blame the network, or simply hand the phone to the other person who actually has the problem.