airpods 2 pro when noise cancellation ON bad mic quality

This seems like that there is something going on. Is the same behavior happening when your restart your paired iPhone?

If so, try and reset the AirPods to see if the issue is persisting

1. Put your AirPods in their charging case, close the lid and wait 30 seconds.
2. On an iPhone or iPad that's paired with your AirPods, go to Settings > Bluetooth:

• • If your AirPods appear in the My Devices list, tap the More Info button next to your AirPods, tap Forget This Device, then tap again to confirm.
  • If your AirPods don't appear in the list, continue to the next step.

1. Open the lid of your charging case.
2. Depending on which AirPods you have, press the setup button on the back of your case or tap the front of the case:

Press and hold the setup button on the back of the case for about 15 seconds, until the status light on the front of the case flashes amber, then white. You can now reconnect your AirPods.

If the status light still doesn't flash white, learn what to do.