If you are experiencing low sound on your iPhone 13, there are a few things you can try to fix the issue:
Check volume settings: Make sure that your volume settings are turned up and that your phone is not in silent mode. You can adjust the volume by using the physical buttons on the side of your iPhone or by going to Settings > Sounds & Haptics.
Clean the speakers: Sometimes, debris or dust can accumulate in the speaker grills, which can affect sound quality. Try using a soft-bristled brush to gently clean the speaker grills.
Restart your iPhone: Restarting your iPhone can often fix minor software glitches that may be causing the low sound issue. Press and hold the side button and either volume button until the power off slider appears. Drag the slider to turn off your device. Then, press and hold the side button again until the Apple logo appears to turn your device back on.
Update your iPhone: Make sure your iPhone is running the latest version of iOS. Software updates can include bug fixes and performance improvements that can help improve sound quality.
Reset all settings: If none of the above steps work, try resetting all settings on your iPhone. This will not delete any of your personal data, but it will reset all of your settings to their default values. Go to Settings > General > Reset > Reset All Settings.
If you have tried all of these solutions and are still experiencing low sound on your iPhone 13, you may want to contact Apple support or visit an authorized repair center