6. Why does sound come out of the smartphone’s speakers even when the E18 is recognized by the smartphone?

A:  1.  USB Audio output may not be enabled.  Select models from e.g. Sony and Meizu have such a system setting.

2. Different smartphones and different versions of firmware on the same smartphone impose different conditions on USB Audio output.  You may try using players that attempt direct USB audio output, such as HibyMusic (https://play.google.com/store/apps/details?id=com.hiby.music), USB Audio Player Pro (https://play.google.com/store/apps/details?id=com.extreamsd.usbaudioplayerpro) or Onkyo HF Player (https://play.google.com/store/apps/details?id=com.onkyo.jp.musicplayer).  If it still doesn't work using these players, it may be assumed that the smartphone hardware supports USB OTG but not USB OTG audio.