So, my mother in law had a haunted iPhone that would only play the ringtone very softly over her hearing aids, or not at all. This is a widely reported problem with no known working solution. (I HAVE TRIED EVERYTHING YOU CAN GOOGLE). Today we migrated her to a new iPhone 16e, and it transplanted the problem from her iPhone 8! I suspect this is a messed up setting with no UI element (anymore). Is there some kind of iPhone registry viewer? Or a way to reset the audio settings to defaults?
@bert_hubert it’s not the thing where, when she is in a call she can set the volume specifically for that output? As in, if I change the volume now outside of a call, it will not do anything for the volume level of the sound _of_ a call.

@Anneke
That’s exactly what I was thinking.

@bert_hubert

@src_esther @Anneke @bert_hubert Yeah, I was gonna suggest this as well: phones have software volume attenuation and Bluetooth headsets also have independent volume attenuation. The iPhone and the Mac present only one volume control for the external device but they only control one of those two things. Funnily, from my experience the iPhone controls software attenuation while the Mac forwards volume up/down to the Bluetooth device's internal volume control.

@src_esther @Anneke @bert_hubert I can easily reproduce this failure mode with a Marshall Bluetooth speaker. First, connect to the Mac and turn volume down. Then, connect to the phone and witness the inability to turn the volume up enough to be usable.

So, my stupid recommendation is to connect the hearing aids to a Mac first and max out the volume. Disconnect, forget device, connect to phone.