Sound is the modulation of physical pressure through a medium- air, water, rock, etc. The human audible modulation range is generally 20hz to 20khz, which is the audio range. The BCX Ultra modulates electricity, which is flow of electrons, in the audio range, below, and above. It also modulates light (photons) and EMF (electromagnetic field). Within the human audio range, electricity is transmitted by physical conduction through an electrically conductive material- not air. The Ultra does not modulate physical pressure- a pressure transducer is required for that. There are different types for different mediums, and the loudspeaker is most common for air.