Disable Automatic Ear Detection
Out the box, the AirPods are programmed to pause when the sensors detect that you have taken one out of your ear. They stop completely when both buds are removed, forcing the audio to play through the connected device's speakers. However, there is a way to disable this feature so the music will play through the AirPods regardless of whether they're in your ears or not.
1. Launch the Settings menu on your iOS device and hit Bluetooth.
2. Select the AirPods.
3. Toggle Automatic Ear Detection to off.
Now, you should have the ability to listen to music with only one AirPod in, which is great if you want to stay aware of your surroundings. Or you can share the other bud with a friend. It's also a great way to charge one AirPod while still listening to music.