The only reason very low frequencies are not normally used for radio communication, is because of the prohibitively long lengths of wire required to make an antenna. If the wire is not long enough, the current arrives at the end long before it is time to reverse and flow in the opposite direction. At high frequencies, the current keeps reversing before the electrons can travel very far in the wire and thus AC current flow is possible in a reasonably short wire. Radio frequencies are always higher than those of sound. When we are taught about the spectrum of frequencies, we tend to get the misconception that radio frequencies are always higher than audio frequencies and that the main difference between an audio signal and a radio signal is their frequencies.
Nothing can be farther from the truth.
The main difference between an audio signal and a radio signal is that an audio signal is vibrating air and a radio signal is a vibrating magnetic field. Radio frequencies are part of the electromagnetic spectrum and sound is part of the acoustic spectrum. Even though Sound and Radio signals involve two separate mediums or spectra, their frequency ranges can certainly overlap. Audio signals in the air can be produced at frequencies well into the multi tens of kilocycles, while radio signals can be produced at frequencies way down into the audio spectrum or lower. As stated above, radio signals in the audio frequency range are less common because of the very long antennas needed to radiate them.