Sound problems when calling or recording video on Xiaomi smartphones are often confusing to users, especially when the interlocutor stops hearing you. Owners of the Xiaomi Redmi 9 model are no exception, and the first step in solving the problem is finding hardware components. Understanding exactly where the recording elements are located is critical for correct diagnosis of a malfunction.
In this guide, we will take a closer look at the architecture of your device’s audio system so you can determine which module is out of order or needs cleaning. Often users look for a single hole without knowing that modern smartphones use a system of multiple microphones, each of which performs a different function.
Not only can hardware be affected, but it can also be used for preventive maintenance. Dust, pile and moisture are the main enemies of acoustic membranes, and regular visual inspection helps extend the life of the device. Next, we will look at the specific locations of components on the Redmi 9 body and how to test them.
Main location of sound modules on the body
The case of the Xiaomi Redmi 9 has two main microphone holes, often confused with dynamic grilles or simply decorative elements. The main microphone, responsible for transmitting your voice during standard phone conversations, is located on the bottom end of the device, it is located in close proximity to the USB Type-C charging connector and 3.5 mm audio output.
The second element, often called noise-cancelling or extra, is on the top end of the smartphone. Many users mistakenly believe that it is an infrared port, but in this model, the IR sensor is combined with the speaker or hidden under the glass, and the hole on top is designed for the secondary microphone, its main task is to capture background noise for their subsequent software elimination during a conversation.
⚠️ Warning: Do not attempt to clean the holes with sharp metal objects such as needles or pins. The microphone membrane is very close to the surface and damage to it will lead to irreversible loss of sound quality or complete loss of sensitivity.
Visually, the holes look like small round or oval cutouts in a metal frame or plastic edging of the body. In the Redmi 9 model, the bottom microphone is often covered with a fine mesh that prevents large dust from getting in, but over time can be clogged with pile from pockets. The top hole is usually more open, making it vulnerable to moisture when using the phone in the rain.
Functional separation: main and secondary channels
Modern smartphones, including the Xiaomi Redmi 9, use stereo recording and active noise cancellation technology, which requires at least two independent audio input channels. The primary Mic is activated by default when you start a phone application or voice recorder in standard mode, which provides the main volume and clarity of the interlocutor's speech.
The second microphone on the top is paired with the main one, which is designed to analyze the environment, and the processor processes signals from both devices and subtracts from the main signal the frequencies that only came to the top microphone (wind, street noise, traffic noise), which allows your voice to sound pure even in a clean environment.
Technical details of noise reduction
When recording video to the rear camera, both microphones are often used to create a stereo effect, if this option is enabled in the camera settings. If you notice that when recording video, the sound becomes deaf or intermittent, the problem may lie in the desynchronization of the two channels.
Detailed diagram: where to look for holes on Redmi 9
To accurately locate components on the Redmi 9 (and its 9A, 9C variants), you should carefully examine the ends of the device. The bottom edge contains a multimedia speaker, a charging connector and two symmetrical holes on the sides of the charging port. The microphone in this area is usually shifted closer to one of the edges, often to the right if you look at the screen, or to the left, depending on the regional version of the build.
The top end is more minimal. There you'll find a 3.5mm headphone jack, an IR port (black glass) and a small round hole. This is the entrance to the top microphone. In some versions of the Redmi 9, it can be hidden under a thin protective mesh integrated into the frame.
| Location. | Appearance | Substantive function | Risks. |
|---|---|---|---|
| Lower end | The hole at USB-C. | Talk, recorder. | Dust, pile, moisture |
| Upper end | Small round hole | Noise suppression | Water, mechanics. |
| Back panel. | Not present (in this model) | - | - |
| Screen. | Hidden under the display | No (in Redmi 9) | Screen-breaking |
Importantly, unlike some flagship models, the Redmi 9 doesn't have a third microphone on the back next to the camera. The entire speaker system is based on two audio entry points. If you're looking for a hole on the back of the phone, you won't find one there, because it's not designed for the budget segment.
Diagnosis: how to check the work of microphones
Before you carry the device for repair or disassemble it, you need to programmatically check which channel is not working. In the MIUI shell installed on the Xiaomi Redmi 9, there is a built-in engineering menu for testing the equipment. To get there, open the Phone app and type the combination ##6484##.
In the CIT menu that opens, you need to find the item associated with the microphone, usually called the Microphone or the Main Mic. After selecting the test, the system will ask you to say something to the phone. If the volume indicator responds to your voice, then the bottom channel is good. To check the upper channel, there can be a separate sub Mic or Top Mic item in the menu.
☑️ Microphone check.
An alternative method of checking is to use a voice recorder: record a voice message by holding the phone to your mouth with the bottom, then the top. Compare the recording quality. If in one case the sound is missing or severely distorted, this indicates a physical problem with a particular module or its contact oxidation.
⚠️ Warning: If the indicator doesn't respond at all in the test in the engineering menu, the problem may not be in the microphone itself, but in the software failure of the drivers.
Causes of sound deterioration and cleaning methods
The most common cause of silent sound or its complete disappearance on the Xiaomi Redmi 9 is banal pollution. Clothing pockets are the source of the pile that tightly clogs the microphone grid. Over time, the compressed dust turns into a cork that physically blocks the sound wave from accessing the membrane, cleaning in this case is the only necessary action.
Use a soft toothbrush or an antistatic brush to clean the stubble safely, you can lightly moisten it with alcohol (isopropyl), but never pour the liquid inside the hole. With careful sweeping motions, remove the contaminants from the mesh surface. You can also effectively use a spray of compressed air, blowing the holes in short bursts.
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Use paint tape: glue sticky tape to the microphone hole and sharply tear off - this will help to pull out surface dust without mechanical impact.
If cleaning didn't work, it could be oxidation of the contacts inside the plume, especially if the phone was in the rain, corrosion of the connector connecting the microphone to the motherboard, requiring disassembly of the device, ultrasound cleaning of the contacts, or replacement of the plume.
Replacement of the microphone: what you need to know
In Redmi 9 design, the bottom microphone is often integrated into the charging socket plume or goes by a separate module soldered to the board. The top microphone is usually a separate element connected through a connector or soldered to the main board. Self-replacement requires skills with a soldering iron and thin electronics.
Replacement requires removing the back cover (it is glued), unscrewing the frame mount screws, disconnecting the battery and removing the motherboard. Microphone soldering requires care, as overheating can damage neighboring components. New parts can be found on sale on request "Microphone Xiaomi Redmi 9" or "charge plume Redmi 9".
If you do not have experience in repairing, it is better to contact the service center. Incorrect installation of a new part can cause the sound to appear, but will be accompanied by a strong crackling or whistle due to poor-quality soldering or defective parts.
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Replacing the microphone in Redmi 9 often requires soldering, as in many revisions it does not have a convenient connector connection.