Sorry but this solution does not work! I encountered this problem after upgrading my imac 27 2017, even after cutting these stripes, the sound quality is still VERY poor (as if you were speak into a pipe), Siri works bad, Skype constantly reduces the sensitivity of the microphone to a minimum (apparently because it registers some noise from inside)
I guess the problem is that the sound from the inside of the imac should not get on the microphone and most likely there are two microphones installed - one for noise canceling the other for capturing sound and they need to be separated, the original strips that Apple uses have a small cutout in the center, insulating the microphone somehow [|https://ibb.co/kABrEo], Dear iFixit I beg you to find a solution to this problem, at the moment it's very difficult to use the built-in microphone
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