Making a normal phone call, holding the phone to my ear, I hear no audio.
If I turn on speakerphone, I hear audio just fine. If I plug in a headset into the jack, I hear audio just fine. All my ringtones and notifications also work fine and I have no problems playing multimedia.
I hadn't actually run into this until just now because I usually use a headset for calls, so it's possible it's been this way since I first received the phone.