Got the new 7.1 nougat update and since yesterday opening the microphone search on the Google bar brings up this can't open microphone error, then it closes. Just tested it on a call and works fine
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It's working in safe mode, soon know it's a 3rd party app. Although I've not installed anything new or changed settings.any advice on narrowing down the culprit app?
It could be something to do with the App Permissions of one of the third-party apps, now causing trouble after the update. You could check those first for each app that might plausibly have permission to use the microphone. Otherwise, work backwards from the last app installed, Disabling or Uninstalling as you go. I hope it doesn't take you too long....and welcome as a new member. 
May I ask how you got 7.1? Are you sure your not confusing 7.1 with the October security update for 7.0?
I was asking myself the same question. The factory image and OTA update haven't posted to the dev site yet (I checked this AM). The only theory I have is that the OP is on the beta channel.
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