Modern Xiaomi, Redmi and POCO smartphones are equipped with a complex noise reduction system that is impossible without the use of two or more microphones. Usually the main sensor is located at the bottom of the case, and the second, additional, is located at the top of the device, often hidden in a narrow hole next to the camera or infrared port. It is this upper microphone that is responsible for suppressing foreign noise during a conversation, recording stereo sound on video and the voice assistant when the phone is lying up.
Users often experience a situation where the interlocutor complains of a quiet voice or echo, or when filming there is no sound, although the main microphone is working. In such cases, there is an urgent need to diagnose the upper microphone to rule out software failure or physical damage. Ignoring the problem can lead to the fact that you miss an important call or record a poor-quality video, so timely verification is critical to maintain the functionality of the gadget.
In this guide, we will look at all the testing options available, from built-in system utilities to third-party applications, how to interpret test results and what to do if a malfunction is detected, and it is important to understand that in most cases the problem is not the failure of the module itself, but contamination or software conflict that can be fixed on your own.
Why you need a second microphone in your smartphone
Many owners mistakenly believe that the top hole is just for beauty or as a backup. In fact, noise reduction works on the principle of comparing signals: the main microphone captures your voice and the surrounding noise, and the top one captures only background sounds. The processor analyzes the difference and subtracts the noise, leaving the clean voice of the interlocutor. If the top sensor does not work, this mathematical operation becomes impossible, and the quality of communication drops sharply.
Also, when you're recording video horizontally, it's the top microphone that often takes the bulk of the audio capture load, especially if you're holding the phone at the bottom. In modern models that support Dolby Atmos or spatial sound, failure of one channel leads to loss of audio volume, so checking the performance of each channel individually is a mandatory procedure in troubleshooting.
⚠️ Warning: Do not seal the upper hole with protective films or cases with poor perforation. This physically blocks the access of the sound wave to the membrane, making the noise reduction system useless.
Understanding the role of each element helps to better diagnose the problem, if you're talking in a quiet room and you're not being heard on a noisy street, that's a direct sign of a fault in the top microphone, but if you're not heard everywhere, the problem can be complex.
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Use the Call Record feature (where permitted by law) to self-test, record your voice in different conditions and see if there is a difference in volume and purity.
Checking through CIT's engineering menu
The most reliable and quickest way to test a smartphone’s hardware is to use the built-in CIT (Customer Interface Test) engineering menu, a tool created by manufacturers for factory diagnostics that allows you to test each module separately, bypassing standard system settings. To enter the menu, you need to open the standard Phone app and type a special combination of characters.
Enter the code ##6484## or ##4636## The menu should open automatically, without having to press the call button. If the code doesn't work, maybe your firmware has operator or region limitations, and then you'll have to use it.-okWe can use alternative methods. CIT Select the item related to Top Mic or Secondary Mic.
☑️ Actions in the Engineering Menu
During the test, the system will ask you to say a few words, and at that moment, it's recording from a specific sensor, and when you're done, you'll hear the recordings play back, if the sound is clear and loud, the module is working, if you hear cracking, silence, or distortion, you need to change or clean, and that's the most accurate method, because it eliminates the impact of third-party applications.
⚠️ Note: Do not change settings in other sections of the engineering menu unless you are sure of their purpose. Accidental activation of certain functions can lead to recalibration of the screen or network.
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CIT’s engineering menu is the only way to check the physical health of the microphone, separating it from Android’s software settings.
Diagnosis with a dictaphone and video
If the engineering menu is closed, you can use standard media tools, the technique is to isolate the sound source, to check the top microphone, you need to create conditions under which the main (bottom) microphone will not be used or its contribution will be minimal. Open the Dictaphone or Camera application.
Put the camera in video mode. Put the top of the smartphone (where the hole of the second microphone is) right to your mouth and speak quietly, while covering the bottom hole (main microphone). Be careful not to close the speaker. Record a short video and play it. If the sound is loud and clear, the top channel works.
- 🎤 Record the video by holding the phone to the top of the sound source.
- 🔇 Close the bottom microphone with your finger while recording to isolate the test.
- 📹 Check the recording in the headphones to hear noises and crackles.
- 🔄 Repeat the procedure in voice recorder mode if the camera does not give a clear sound.
It is also useful to compare recordings made in a horizontal and vertical position. In some MIUI firmware, the microphone switching algorithms may not work correctly when rotating the device. If the sound is only coming from one side in horizontal mode (when watching video), or if it is not, this is a clear symptom of a problem with the upper channel.
Why can a recorder write quietly?
Use of third-party applications for the test
When built-in tools aren't enough, Google Play comes to the rescue, and apps like Mic Test or Sound Meter let you visualize the incoming signal in real time, which is especially convenient because you can see the sensor's response right away, without having to constantly overwrite files.
Install an application, such as "Mic Test" or "Audio Recorder." In the application settings, you can often select the audio source. MIC_TOP or VOICE_RECOGNITION, If you have this option, you can force the top sensor to be activated. Watch the graph: when you talk near the top, the graph should fluctuate actively.
| Annex | Type of check | Pluses | Cons |
|---|---|---|---|
| Mic Test | Visual graph | Instant result | Advertising in the free version |
| Test Your Mic | Recording and reproduction | Simple interface | I don't always see the second channel. |
| Phone Doctor Plus | Integrated diagnostics | Checking all sensors | It takes a lot of permission. |
| Sound Meter | Measurement of the dB level | Accurate volume measurements | Hard for beginners. |
Using third-party software gives you more flexibility, but keep in mind privacy. Give apps access to only the microphone, avoiding unnecessary permissions for contacts or gallery. If the app shows activity when silent, maybe there is a background process in the system that uses the microphone all the time.
Programmatic causes of malfunction
Before you carry your phone for repair, you need to rule out software failures. Often after updating your MIUI or installing a new application, the audio stream settings may get lost. First, check the permissions. Go to Settings → Apps → All applications, find an application that doesn't have sound (such as Telegram or Recorder), and make sure that access to the microphone is allowed.
The second important step is safe mode. If the top microphone stops working after installing a program, it can conflict with the system audio driver. Load the phone into Safe Mode (usually by pressing the off button on the screen, then by long tapping the "Off" button). If this mode is running, look for the culprit among the newly installed applications.
It is also worth checking the special features settings. Features for people with disabilities, such as “Sound Improvement” or “Mono-audio”, can redirect signals incorrectly. Try resetting the audio settings to factory or perform a full reset (with a pre-backup) if the problem is systemic.
⚠️ Note: Factory Reset will delete all your data. be sure to back up photos and contacts before doing this.
Physical damage and cleaning
The most common, but common, cause is pollution: the top microphone mesh is very shallow and easily clogged with dust, skin fat, or pile from your pocket. Over time, this forms a dense plug that muffles the sound. Use a soft toothbrush or a special sticky tape to clean. It is strictly forbidden to use sharp objects (needles, pins) to pick through the hole, since you can pierce the microphone membrane that is just behind the net.
If cleaning didn't work, check the case for signs of falling or getting moisture. Even if the phone has IP53 or IP68 protection, the leakage is broken over time. The ingress of moisture causes the contacts to oxidize on the microphone plume. Visually, this may be invisible, but the sound will disappear or crack.
- 🧹 Carefully clean the hole with a dry soft brush.
- 💨 Blow the hole (cautiously, without saliva) or use a pear.
- 🔍 Check the net for dents from falls.
- 🌡️ Check if the upper part of the body is overheating (sign of KZ).
In the event of physical damage (impact, water), software methods will not help. Requires disassembly of the device and replacement of the module. In Xiaomi smartphones, the top microphone is often made as a separate small module on a flexible plume or soldered into the connector board, which requires skilled repair.
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90% of problems with the quiet sound of the upper microphone are solved by simply cleaning the mesh from dirt and grease.