Android Notification Sound

[omeriko]

In the documentation of the : Android Notification Sound item there is am example of the config.xml entry:

<platform name="android">
    <resource-file src="res/android/raw/my_sound.mp3" target="app/src/main/res/raw/my_sound.mp3" />
</platform> 

with the my_sound.mp3 file

but when you give the notification payload example few lines later:

{
  "name": "my_notification",
  "notification": {
    "body": "Notification body",
    "title": "Notification title"
  },
  "android": {
    "notification": {
      "sound": "crystal"
    }
  }
}

you indicate filename called : "crystal".

it's confusing.