Today I saw a guy repeating something that Siri had misunderstood. He had turned his iPhone on its end and was speaking into the bottom of it where, presumably, he thought the microphone is located. Therefore Siri would be better able to hear him.
He was right. But very wrong too.
An iPhone has THREE microphones. One’s in the bottom, where our guy thought. One’s in the small speaker assembly that you hold near your ear while making calls, and one’s on the back near the camera. This is so your iPhone can listen no matter how you hold it, and also to aid noise cancellation.
The mic on the back is the one that listens for Siri, with help from the front ear speaker mic. So, if you suspect Siri is going deaf then take a look at these and CAREFULLY clean ‘em. Canned air is the best for this kind of thing. DO NOT STICK ANYTHING IN THE HOLES (and you can make your own suggestive comment here).
But if you want to talk to Siri and have it hear you normally, just talk at the screen. That’s using the phone how Apple intended you to. Don’t turn the phone around and speak directly the mic, and don’t turn it upside down. In all likelihood this will make your voice sound distorted to Siri.