How to use your iPhone or iPad as a remote microphone
This functionality lets you use an iOS device as a remote microphone, so you can place your device near a person speaking across a room and the sound is streamed to your hearing aids.
Tap the Sound icon at the bottom left of your screen (on the tab bar) to access sound controls.
Tap the three dots to bring up more options.
Tap the microphone icon to bring up the remote microphone text and then toggle the remote microphone capability on or off.