When playing any King games, you have the chance to turn the sound of the game on or off.
You can check and change this within the app. When entering the game, please locate the gearwheel menu, and there are two options that have to do with sound.
One is a music note, which will turn on or off the music in-game. And the other option is a speaker icon that is in regard to other sound effects. For example, voices or special effects.
To receive the sound as desired, please be sure these are both enabled. You can always decide to have one enabled, and disable the other. It's your choice!
After these two options are enabled, you can then use the volume up and down buttons on the side of your device to control the volume level for your comfort.
If you notice both of these are on but you are still not receiving sounds in-game, please test other apps or media on your device to ensure sound is being heard from other content to see if it may be a system or hardware related.