Re: "Single AirPod having connection issues :
The audio is quiet or crackly, as if it’s been bass boosted to the extreme".
First of all: You may want to check whether both the iPhone and the Aitpods have up-to-date software:
Eg: Firmware updates often contain bug-fixes and improvements
More info: About firmware updates for AirPods - Apple Support
To check for newest available iOS version(s) on iPhone : See : Settings > General > Software updates
If you choose to update iOS : It is always wise to back-up iPhone first
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If software is already up-to-date, or if the situation continues after updating:
There are various possible causes / solutions / for the situation. We need to find the cause in your case.
Wondering if Apple support's trouble-shooting articles (links below) can help find the source of the problem:
(1) See: If your left or right AirPod isn't working - Apple Suppor
Eg says:
"Find out what to do if there’s no sound in one AirPod, or if one AirPod is louder or quieter than the other."
(2) Ensure nothing (eg: wax or speck of dirt) is blocking or interfering with microphone or speaker openings.
How to clean your AirPods - Apple Support
(3) Re: "crackles" : You may want to make sure the "fit" is just right for you
Find the right fit with AirPods 3 or 4 - Apple Support
(4) See what to do: If the sound from your wireless headphones cuts out or is distorted - Apple Support
Eg: says:
"Improve your Bluetooth connection : Your headphones communicate using Bluetooth,
and a Bluetooth signal can be interfered with or weakened in some situations."
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Other resources:
AirPods Support Website: (topics, resources, and contact options etc.)
AirPods Support - Official Apple Support
And
AirPods User Guide: AirPods User Guide - Apple Support
