The BlindSquare sounds only work as long as your iPhone has not been muted. Please check if the mute switch of your iPhone is in the position where it is closer to the screen of the device and slide it into this position if necessary.
Please also check that sounds are selected under Other, Settings, BlindSquare Sounds. On the bottom of this screen you will find a switch letting you select all of the sounds as well as a slider to set the volume of the sound. Try setting the volume to 100 percent and see if that helps. If you wish, you may later decrease the volume of the sounds to your prefered setting.