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Okay, I did a real-world test with noise cancelling with a BookBook 6 cut to fit an iPhone 7. This is using the phone to call an iPhone 6 on T-Mobile, which I believe has enhanced audio quality (sounds like it, anyway), and a TV on as background noise:

With the case folded over against the back of the phone, it sounds perfectly fine. Quite clear.

With the case wide open and not against the back of the phone, it sounded similar. If anything, it actually sounded slightly worse.

Result: At least in my test, noise cancellation problems caused by talking on the phone with the case folded back on itself over the rear microphone are somewhere between not significant and nonexistent.
 
As usual, those that are not the target audience have to chime in massively to crow about the fact that they are not the target audience. And those that live loose and crime-filled lives dismiss a product because it won't work in their city.

All that said, I've used the BookBook since the iPhone4s and found it uniquely does the job of combining wallet and phone holder better than any other solution. There is nothing else that does this, this well.

The only weakness is the spine's material wears out after a few years if you slide the phone in and out of your front jeans pocket multiple times a day.

For the exposed cards, I fold the flap all the way around to the other side, and my hand that holds the phone has that in its palm - nothing to see there. And the new generations of cards don't have numbers on the front it seems, so thats less of an issue. Thought there is no solution to someone not keeping track of their phone/wallet or behaving like a fool in a crime ridden city.
 
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