Not all the sounds are equal. Without measuring will be impossible to determine in an objective way, the characteristic of a specific sound. In this game, you will need yo compare certain sounds with the one that its defined as the threshould between LOW (?) and HIGH (?) sound. Placing the mouse on the botton images (the targets) you will be able to hear how LOW, the THRESHOULD and HIGH sounds sounds!!!
If you click in the upper image, the sound that need to be match with one of the targets, you will hear the sound (and see the shape of the sound too!!) To select where the unselect sound belongs, click on the target sound you believe it belongs. GOOD LUCK