Quincke's interference tube demonstrates (with surprising reliability) sound interference. They are designed such that one arm is one-half wavelength longer than the other for sound waves of frequency 256 Hz, so sound at that frequency undergo totally destructive interference through the tube. A tuning fork can reliably create the sound for the experiment. Compare the sound through the interference tube from the 256 Hz tuning fork (or lack thereof) with other tuning forks.
