Hi Mabaspy,
Welcome to the Apple (user-to-user) Community!
Re: "AirPod Pro2. When using it as a hearing aid I cannot get rid of an echo effect." " How can I improve on this?"
If you haven't already:
✽ You may first want to browse through Apple Support's online article to see if any of the tips there help
eg: Check if you set-up the AirPods as suggested
Use the Hearing Aid feature on your AirPods Pro 2 - Apple Support
✽ You may want to experiment with the microphone settings to see if that helps find what works best for you.
Change the settings of your AirPods and AirPods Pro - Apple Support
Eg: says:
"Set Microphone to left, right, or automatic
There's a microphone in each AirPod, so you can make phone calls and use Siri. By default, Microphone is set to Automatic, so that either of your AirPods can act as the microphone. If you're using only one AirPod, that AirPod will be the microphone.
You can also set Microphone to Always Left or Always Right. You can also set Microphone to Always Left or Always Right to always have either the right or the left AirPod use the microphone even if you remove it from
your ear or put it in the case."
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If still needing a solution: Resetting the AirPods may help.
How to reset your AirPods and AirPods Pro - Apple Support
Eg: says:
"You might need to reset your AirPods if they won't charge, or to fix a different issue."