One of the nicest features of iOS7 is that Apple allows developers to choose whether their application uses the internal microphone (built into the device), or an external microphone (usually along the earbud cable). Our app, EarMachine, allows the user to choose which microphone they are using -- see Image above. In general, we have observed that sound quality (and audio calibration) is FAR better when using the built-in microphone.
We have also observed that many users don't know where their microphone is located. If you are using an iPhone the built in microphone is on the bottom of the device (next to the 30-pin or lightning jack). You can test this out for yourself by gently tapping on different places of your iPhone while listening through the built-in mic.
So, if you are using EarMachine and holding your iPhone upright, the microphone will be pointing downward. We recommend that you turn your phone upside down. We designed EarMachine to automatically rotate so that the UI is right-side up when the phone is upside down. Then you can point the microphone at whatever sound you are trying to hear.
Note that this does not apply to iPod. On those devices, the microphone is toward the top, near the rear-facing camera, so it is best to hold the phone upright.