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In order to radiate and intercept energy efficiently, the physical size of the transmitting and receiving antennas must be an appreciable portion of the E & M wavelength.
An electromagnetic wave at an audio-frequency ... let's say 1 KHz ... has a wavelength of
( c / 1,000 ) = ( 3 x 108 / 103 ) = 3 x 105 = 300 kilometers = about 186.4 miles
Even at the nominal limit of the frequency range of hearing ... say 20 KHz ... the wavelength is
( 3 x 108 / 2 x 104 ) = 15 kilometers = 9.3 miles.
In order to have a fighting chance of successful radio communication at audio frequencies, over reasonable distances using reasonable transmit-power, the parties at each end of the link need antennas measured in miles.
There are plenty of other great reasons that we don't use radio at the physical baseband frequencies; but even of there were no others, this reason alone is a pretty potent show-stopper.
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