What to do if Galaxy S9 Plus sounds like it is underwater or in tunnel during calls

This post addresses a common issue for the Galaxy S9 and S9 Plus: Galaxy S9 Plus sounds like it is underwater or in tunnel during calls. If you happen to encounter this issue on your own device, learn how to deal with it by following our suggestions below.

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Problem: Galaxy S9 Plus sounds like it is underwater or in tunnel during calls

I have a S9+. When on a phone call, if my mouth is not right in front of the speaker, the other person can’t hear me. I can never hold phone with my shoulder for a second etc. Also, when using speaker phone, they often say I sound like I’m in a tunnel or under water. HELP! It’s driving me crazy!

Solution: There are a number of variables to consider when identifying the cause of this problem. Below are the troubleshooting steps that you can do.

Forced restart

Refreshing the system is often a simple way to fix bugs. If you haven’t tried this yet, follow the steps below on how to simulate  the effects of pulling out the battery. In older phones, removing the battery is recommended to clear the system. Since your Galaxy S9 Plus has non-removable battery pack, you can only simulate the effects of physically disconnecting the battery. Here’s how to do that:

  1. Press and hold the Power + Volume Down buttons for approximately 10 seconds or until the device power cycles. Allow several seconds for the Maintenance Boot Mode screen to appear.
  2. From the Maintenance Boot Mode screen, select Normal Boot. You can use the volume buttons to cycle through the available options and the lower left button (below the volume buttons) to select. Wait for up to 90 seconds for the reset to complete.

Clear cache of Phone app

If the problem only occurs during calls, it’s possible that there’s a problem with the Phone app cache. Try refreshing the cache with these steps:

  1. Open Settings app.
  2. Tap Apps.
  3. Tap on More settings at the upper right (three-dot icon).
  4. Select Show system apps.
  5. Find Phone app and tap it.
  6. Tap Storage.
  7. Tap Clear Cache button.
  8. Restart your S9 and check for the problem.

Clear data of Phone app

Should nothing change after clearing Phone app cache, go ahead and clear its data instead. Here’s how:

  1. Open Settings app.
  2. Tap Apps.
  3. Tap on More settings at the upper right (three-dot icon).
  4. Select Show system apps.
  5. Find Phone app and tap it.
  6. Tap Storage.
  7. Tap Clear Data button.
  8. Restart your S9 and check for the problem.

Clear cache partition

At times, bugs can be the result of a corrupted system cache. To ensure that this cache is in top shape, make sure to clear the cache partition from time to time. Here’s how:

  1. Turn off the device.
  2. Press and hold the Volume Up key and the Bixby key, then press and hold the Power key.
  3. When the green Android logo displays, release all keys (‘Installing system update’ will show for about 30 – 60 seconds before showing the Android system recovery menu options).
  4. Press the Volume down key several times to highlight ‘wipe cache partition’.
  5. Press Power button to select.
  6. Press the Volume down key until ‘yes’ is highlighted and press the Power button.
  7. When the wipe cache partition is complete, “Reboot system now” is highlighted.
  8. Press the Power key to restart the device.

Reset app preferences

Voice calling apps usually depend on core default apps and services to work properly. To see if there’s a disabled default app or incorrect default app setting, you can reset all app preferences. Follow these steps in order to do that:

  1. Open Settings app.
  2. Tap Apps.
  3. Tap on More settings at the upper right (three-dot icon).
  4. Select Reset app preferences.
  5. Restart your S9 Plus and check for the problem.

Check microphone

If the problem remains at this point, there’s high likelihood that your phone’s microphone may be to blame. To check if that the case, you can try to record your voice and listen to the recording afterwards. If your voice sounds bad or as if you’re in a tunnel, that’s a confirmation that the microphone may be the problem.

To record your voice:

  1. Open Voice Recorder app. This is a Samsung app so if it’s not readily available in your Home screen, try looking for your Samsung folder.
  2. Tap the red Record button and try to record yourself for at least 20 seconds.
  3. Stop the recording.
  4. Save the recording.
  5. Listen to your voice.

If your recorded voice sounds bad, try to factory reset your phone. Afterwards, record your voice again when there are no apps installed. If there’s no change, you can assume that the phone’s microphone may be damaged or malfunctioning.

NOTE: Sometimes, water or moisture in the microphone ports may muffle the sound coming in. if your S9 Plus was exposed to water or moisture before this problem started, be sure to wipe it with clean, soft cloth and air dry it properly. Water naturally evaporates in room temperature after a few hours so leaving the phone in a room may be enough. Alternatively, you can leave the phone dried by putting it in a bag of rice for a couple days.

Factory reset

Wiping the phone and returning its settings to defaults may be a necessary step to confirm whether or not there’s hardware malfunction. Factory reset is effective in fixing software bugs so if the problem remains after returning all settings to their defaults, you can assume bad hardware is to blame.

To factory reset your S9 Plus:

  1. Create a backup of your data.
  2. Turn off the device.
  3. Press and hold the Volume Up key and the Bixby key, then press and hold the Power key.
  4. When the green Android logo displays, release all keys (‘Installing system update’ will show for about 30 – 60 seconds before showing the Android system recovery menu options).
  5. Press the Volume down key several times to highlight ‘wipe data / factory reset’.
  6. Press Power button to select.
  7. Press the Volume down key until ‘Yes — delete all user data’ is highlighted.
  8. Press Power button to select and start the master reset.
  9. When the master reset is complete, ‘Reboot system now’ is highlighted.
  10. Press the Power key to restart the device.

Contact carrier or Samsung

Depending on which option works best for you, you can either get hold of Samsung for repair or your carrier for network troubleshooting or phone replacement. If the issue only occurs while doing voice calling, there’s a chance that the issue may be network-related. Be sure to let your network operator know so they can help you troubleshoot.


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