It appears that your AirPods volume isn't working as expected. You're able to hear sound when the volume is at 60%, but it's still too quiet. Anything below 60%, and you're unable to hear at all. I'm happy to help.
Use your AirPods -- Follow the steps below to use the Setup button to reset your AirPods. Once it's completed, test the issue.
If you don't see the setup animation when you try to set up your AirPods with your iPhone, follow these steps. After each step, try to set up your AirPods again.
- Make sure that your AirPods are charged.
- Close the lid, wait 15 seconds, then open the lid. The status light should flash white.
- If the status light doesn't flash white, press and hold the setup button on the back of the case until you see the status light flash white.
- Still can't set up your AirPods? Press and hold the setup button for at least 15 seconds, until you see the status light flash amber a few times and then flash white.
Apple - Support - Product Selection -- If the issue persists, Apple Support will be able to troubleshoot this issue further with you. They also can supply you with all of your service options, if needed.