Short answer
Forget and re-pair the device, update its firmware, and reset network settings if problems continue.
After moving to a new phone, Bluetooth accessories sometimes need a clean re-pair.
Fixes
- Turn Bluetooth off and on from Settings (not just Control Center).
- Settings › Bluetooth › tap ⓘ › Forget This Device, then pair again.
- Update the accessory — AirPods update automatically when connected and charging; car systems may need a dealer update.
- For CarPlay, remove the car in Settings › General › CarPlay and set it up again.
- Restart both devices.
- Reset Network Settings as a last resort.
Audio crackle?
Some iPhone 18 Pro owners report crackling from the built-in speaker that isn't Bluetooth related. See our iPhone 18 Pro problems tracker.