Comprises two matched nickel plated tuning forks of frequency A(426.6), each mounted on top of hollow wooden box open at one end. One fork is provided with a sliding mass on one prong by means of which its frequency can be varied from the nominal 426.6Hz. When both forks are sounded a clearly audible beat is produced, its rate depending upon the difference in frequency between the forks.
* Pair of Tuning Forks on Resonance Boxes
