In 1839 physicist Heinrich Wilhelm Dove discovered when audible signals of two different frequencies are listened too separately, one to each ear, for example a frequency of 105 Hz is heard to your right ear, and a frequency of 100 Hz is heard to your left ear, your brain hears a third frequency
In 1839 physicist Heinrich Wilhelm Dove discovered when audible signals of two different frequencies are listened too separately, one to each ear, for example a frequency of 105 Hz is heard to your right ear, and a frequency of 100 Hz is heard to your left ear, your brain hears a third frequency