Have you ever been somewhere loud and had to cup your hands over someone else’s ears to tell them something? That is acoustic coupling. And it’s basically what Noopl wants to do with your iPhone except rubber couplers take the place of your hands. Noopl's performance depends on having as tight a seal as possible to block the noisy signal and provide clear sound transmission between the Noopl device and microphone on the bottom of your iPhone.
Let’s first take a look at a Noopl with the proper coupler. Notice the tight seal between Noopl and the bottom of the iPhone:
Compare the previous picture with the next example of a Noopl with poor coupling. Pay attention to the big gaps between the coupler and the bottom of the iPhone:
The coupler pre-attached to your Noopl is designed to work with phone cases. If you don’t use a phone case, there are other couplers in the Noopl box which you'd use instead — different couplers for different iPhone models.