The project Binaural Beat Machine has had several iterations. The prototype above arranges two speakers at the ends of a spinning arm. The two speakers are generating the same identical frequency. Due to the Doppler effect and the design of the object, beats are produced as the speakers alternate in amplifying and negating each other. The experienced effect depends entirely on your proximity to the object. 

My hope is to refine this design and eventually use blown glass resonators instead of speakers.