It probably should be your own device; the audiogram ends up in the iPhone's health app. It can probably be done by someone else if they don't care and don't need to apply a different audiogram for themselves.
That is some nice integration. Having one’s own up to date audiogram stored in a health record and available to doctors and devices.
I was able to use my partner's iPhone to configure some settings.
It's frustrating that the settings can't be changed on Android, and macOS seems to have a subset of settings compared to iOS.