when someone sings they produce sound waves. these sound waves can tell us a couple of things. in looking at the space or period between the waves allows us to see if a person is hitting high or low notes. also, the high of the waves tells us information about how someone is singing. if the waves are high, then someone is singing in a loud pitch, but if the waves are small/short, then they are singing in a soft pitch. you can also tell if someone is singing harsh or smoothly due to the sound waves they produce. if the waves look like a parabola then they are singing smoothly. but the more jagged/ pointed the lines are the harsher the person is singing.