I have no sound in the app!
In the app, please check that you have sounds enabled in the Settings.
In the device's Settings, go to the "Sounds" tab. Then, in the "Ringer and Alerts" frame, move the slider to the middle and activate "Change with buttons".
Now check if you have sounds in our chess app.
If you don't, you need to restart your device: press and hold the button located at the top until "Slide to power off" appears. Slide the red arrow so your device turns itself completely off. When the screen is completely dark, press and hold the same button for one second. Your device will restart.
If you still have no sound in our chess app, then you are hit by a known bug of iOS (the iPad is the worst offender): some apps, for absolutely no reason, cannot emit sounds at all. Then sometimes the problem fixes itself after a while, again for no apparent reason.
People have reported success after rebooting their device several times, or after deleting then re-installing the app (you will NOT be charged for reinstalling, even if you have to enter your Apple password).