A modem used for communicating data. The modem may include a packet generator and modulator. The modulator may include an electronic device configured to select at least one frequency from at least three or more candidate frequencies. At least one oscillator may be in communication with the electronic device and configured to generate respective oscillation signals in response to receiving the frequency(s) from the electronic device. A computational element may be in communication with the oscillator(s) and be configured to receive the oscillation signal(s) and produce a modulated audio signal based on the oscillation signal(s).