All PEMF machines use frequencies that are in the hearing range, so by definition they are all audio frequencies. So yes, technically we are using a signal Generator (software loaded on a tablet, laptop or smart phone) to send an audio frequency (or set of frequencies) through the amplifier and out to the coil which then becomes an electromagnet with a field at the frequency being sent to it. This is pretty much how all of the higher powered brands work...the Sentient ELEMENT, the Doug Coil, the AmpCoil, and the PEMF8000. The lower powered brands are similar except they use capacitive discharge to create the frequencies (even though they are still "audio" frequencies). This method also works but is greatly limited in the amount of gauss that can be produced, which in turn limits the strength of the magnetic field as well as the range of frequencies that it can reproduce. This is why the lower powered brands all use a limited number of onboard frequencies to choose from. With the higher powered brands, you can send any frequency to the unit. The Doug Coil does this with a series of switches on the frequency generator module, the AmpCoil does it with the BetterGuide app, not sure exactly how the PEMF8000 does the frequency generation, and the Sentient ELEMENTallows you to use any app or program you want to create the frequencies you want to use. Ours allows the widest range of frequency options, both in terms of what the frequency is, and in terms of how it's generated. The AmpCoil, for example, comes with a tablet that has the BetterGuide app pre-loaded on it. We let you use any device you want. The AmpCoil only runs frequencies it chooses based on their BS voice analysis. We let you use any frequency you want.