OnePlus
Enable or Disable Hearing Aid Compatibility (HAC) auf OnePlus
Hearing Aid Compatibility (HAC) changes how your OnePlus phone routes audio through the earpiece during a call. Standard call audio can create interference or a faint buzz in telecoil-equipped hearing aids, because the signal isn't shaped for that kind of pickup. Turning HAC on adjusts the earpiece output so hearing aids receive a cleaner, more compatible signal.
You find this option inside the Phone app itself, not in the general system settings. Go to Open the Phone app ➔ Open the menu ➔ Open the Settings ➔ Tap on Accessibility ➔ Enable or disable Hearing aids.
Leave HAC off if you don't use a hearing aid and calls already sound normal through the earpiece or speaker. Turning it on without a compatible hearing aid can make the earpiece sound slightly different during regular calls, since the audio processing is optimized for telecoil pickup rather than direct listening.
Not every hearing aid model supports this feature the same way. Check with your hearing aid manufacturer or audiologist to confirm your device is certified for HAC before relying on it as your main fix for call clarity.