In this acoustic experiment, two Y-shaped glass tubes are connected by two flexible latex tubes of different lengths. Hold a struck tuning fork at the end of one of the Y-tubes and the waves flow down to where the tubes divide. This apparatus makes the waves in one half of the fork in the Y-tube travel half a wavelength farther than the waves in the other half of the fork. When the waves meet in the other Y-tube, they’re in opposite phase to each other, so they cancel each other out. This results in no sound at all. If you disconnect one of the latex tubes, the sound reappears. This apparatus can be used at 256Hz or 512Hz by adjusting the length of the longer latex tube. Use of this apparatus requires a 256Hz or 512Hz tuning fork (not included).