Owners of the Redmi Note 9 series often face situations when the interlocutor complains of poor hearing, or when recording video is completely absent. In such cases, the first question arises about the physical location of the recording elements. Understanding where the microphone is on the Xiaomi Redmi Note 9 phone is key to self-diagnosing malfunctions or conducting preventive cleaning of the device.
Modern smartphones are equipped with not one but several microphones to ensure noise reduction and high-quality recording of stereo sound. In the Redmi Note 9, Xiaomi engineers implemented a complex sound recording system that requires careful study before any intervention. Improper cleaning or attempt to replace without knowing the exact location can lead to irreversible damage to the plumes and circuit board.
In this article, we will take a closer look at the architecture of your gadget’s acoustic system, how to distinguish the top and bottom modules, what tools will be required to maintain them, and how to programmatically check the performance of each of them, which will be useful for both ordinary users and beginner repairmen.
⚠️ Attention: Any actions to disassemble the case of the smartphone automatically deprive you of an official warranty. If your device is in warranty service, contact an authorized service center.
Architecture of the Redmi Note 9 acoustic system
Xiaomi Redmi Note 9 has two main microphones located on opposite ends of the case, a configuration that is necessary to implement a noise reduction function that cuts off background noise during a conversation, leaving the speaker's voice clear. The first, the main microphone, is responsible for transmitting your voice during calls and recording voice messages in messengers.
The second, an additional microphone, performs a secondary function: it analyzes the environment and background noise, allowing the Qualcomm or MediaTek processor (depending on the regional version) to filter the audio stream. In addition, this module is activated when recording video, providing stereo sound if the corresponding function is enabled in the camera settings. Without the correct operation of both elements, the quality of communication drops dramatically.
It is worth noting that in some versions or in deep disassembly you can find mention of the third channel, but in the standard custom build Redmi Note 9 two: they are connected to the motherboard through special connectors or soldered directly to the board, which complicates the procedure of replacement at home.
- 🎙️ Lower microphone – the main channel of voice transmission during conversation.
- 🔊 Upper microphone – noise reduction channel and stereo recording.
- 📱 Double microphone system is the standard for modern mid-range smartphones.
Where is the bottom (main) microphone?
The main sound pickup element in the Redmi Note 9 is located at the bottom of the case, next to the USB Type-C charging connector. If you flip the phone down, you'll see a central hole that is often mistaken for a speaker. In fact, it's part of the speaker system, closed by a protective mesh.
Inside this hole, under the protective membrane, is the microphone module itself, which is protected from dust and moisture by a filter that can eventually get clogged, and this element is most often affected by contamination, because it is in active contact with hands, pockets and bags, visually it looks like a small black dot in the depths of the hole.
To access it, you need to take the bottom of the smartphone out of the back and unscrew the board, but you need to use external methods to clean it, and it's important not to use sharp objects like needles or pins, because they can easily damage the inner membrane, which will lead to complete loss of sound.
☑️ Cleaning the bottom microphone
Often users confuse the microphone hole with the main speaker holes that are located on the sides of it. The speaker is responsible for the output of the sound (music, voice of the interlocutor), and the microphone is responsible for its input. In the Redmi Note 9 model, the microphone hole is usually one and located strictly in the center of the lower end, or symmetrically on one side of the charging port, depending on the regional version of the device.
⚠️ Warning: Never use a vacuum cleaner to clean your microphone. The static electricity it creates can knock out sensitive electronics.
Location of the upper (secondary) microphone
The second microphone, often referred to as the top or optional, is located on the top end of the smartphone. In the Xiaomi Redmi Note 9, engineers hid its hole next to the infrared port (IR port) and the headphone jack 3.5 mm. This is a small, barely noticeable hole with a diameter of about 1 millimeter.
The main purpose of this element is to analyze noise, and when you hold your phone to your ear while you're talking, the top microphone hears the environment, and if you're in a noisy place, the processor subtracts that noise from the main audio stream, and when you record video to the camera, that microphone captures sound from behind the device, creating surround sound.
Users often forget about the existence of this hole and seal it with protective glass or covers that do not have the appropriate cutouts. This is a critical mistake, since closing the upper microphone leads to the fact that the noise reduction system begins to work incorrectly, sometimes completely drowning out the speaker’s voice, mistaken for background noise.
- 🔍 Location: Upper end, next to the IR port.
- 🎥 Function: Stereo sound recording and noise cancellation.
- 🚫 Risk: Closing a case without a cutout blocks the system.
When diagnosing sound problems, make sure to check if the top hole is clogged with dust or pile from clothing. small size, it (very easily) clogs. Careful soft brushing can restore the device to its former clarity. Don't try to pick the hole with a toothpick - the risk of damaging the net is very high.
Why is the microphone called a noise maker?
Diagnostics of microphone malfunctions
Before you start physical cleaning or disassembly, you need to make sure that the problem is in the hardware, not the software failure. In the MIUI shell on which the Redmi Note 9 is based, there is a built-in engineering menu for testing equipment, which allows you to check each module separately.
To enter diagnostic mode, dial ##6484## in the phone book. Once you enter the combination, the CIT (Customer Information Test) menu will open. In the list of tests, find the "Main Mic" and "Sub Mic" items.
If you can't hear you in the Main Mic test, but Sub Mic works (or vice versa), it indicates a physical malfunction of a particular module or its plume, and if both microphones don't work, the problem may be a software conflict, drivers, or damage to the motherboard after a drop or moisture hit.
| Type of test | Code/The Way | What we check. | The result is OK. |
|---|---|---|---|
| Engineering menu | ##6484## | All sound modules | Green Pass button |
| Dictaphone | Annex "Record" | Vote recording | Clear sound without cracking |
| High-profile communication | Call to caller | Operation of both microphones | The interviewee hears clearly |
| Video recording | Camera. | Stereosound | The sound changes when you turn. |
It’s also worth checking your application permissions. Sometimes, after updating MIUI, messengers (WhatsApp, Telegram, Viber) lose access to the microphone. Go to Settings → Apps → All apps, find the right messenger and make sure that the Microphone slider is activated. This is a common cause of a “breakdown” that is solved in a minute.
Cleaning and maintenance methods
If the diagnostics show that the microphone is working but is quiet, or if there is interference, it's likely that the holes have been clogged with dust, skin fat or pile. Cleaning is a delicate process. Use a dry soft toothbrush to begin with. Walk through the openings of the bottom and top microphones in light circular movements.
To clean it deeper, you can use a special spray to clean the electronics or isopropyl alcohol. Importantly, don't pour the liquid directly onto the phone! Wet the cotton swab, squeeze it slightly, and gently wipe the area around the hole. The liquid should not leak into the housing.
Another effective method is to use a sticky tape (scotch) or plasticine, glue the sticky part to the hole and pull it off abruptly, and this will help pull out dust that has settled deeper than the grid. Repeat the procedure several times. If the situation hasn't improved after cleaning, it's possible that the microphone membrane is physically damaged.
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Use paint tape instead of regular stationery. It has a less aggressive adhesive layer and will not leave sticky marks on the body of the smartphone.
In cases where the microphone stopped working after the phone hit the water, cleaning may not help, moisture may have oxidized the contacts on the board, in which case you need to turn off the device as soon as possible and take it to a service for professional cleaning in an ultrasonic bath.
Replacement of the microphone: difficulties and nuances
Replacing the microphone with the Redmi Note 9 is a complex procedure that requires soldering skills and a microscope. Unlike older push-button phones, here the microphone is often soldered directly into the board or connected through a very thin plume that is easy to tear when opened sloppy.
If you decide to repair yourself, you will need:
- 🔧 Set of screwdrivers (cross, starlet).
- 🌡️ Thermal dryer or heating pad for heating glue.
- 🔌 soldering station and flux.
- 🆕 Original spare part (microphone module).
The process starts by heating the perimeter of the back cover to soften the glue, and when the lid is removed, all the screws that hold the plastic frame and the motherboard are unscrewed, and only when you get to the board, you can see the soldering location of the microphone. The bottom microphone often has to remove the charging connector itself, because they can be combined into one module.
⚠️ Warning: The board cannot be overheated when soldering the microphone. Prolonged exposure to temperatures above 300 degrees can detach tracks or damage adjacent components.
If you're not sure about your abilities, you'd better order a replacement service from a service center. Parts are relatively inexpensive, but work requires jewelry precision. Poor soldering will cause the new microphone to languish or malfunction.
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In 90% of cases, the sound “lost” on the Redmi Note 9 is solved by simply cleaning the microphone grid or checking the settings of application permissions, rather than expensive repairs.