There is a lot of discussion going on about the benefits of square waves vs. sine waves for frequency applications. For generation of maximum effect on pathogens when you have the correct frequencies, square waves work best. For direct application of electrodes, positive offset square waves should be used. This will shorten the time needed to eliminate pathogens because (1) square waves are more disruptive to the pathogen and (2) square wave harmonics aid in eliminating them. This is true for primary frequencies and scalar octaves.

Wikipedia has an excellent discussion of square waves.

Square wave

A square wave is a basic kind of non-sinusoidal waveform encountered in electronics and signal processing. An ideal square wave alternates regularly and instantaneously between two levels, which may or may not include zero.

Origins and uses

Square waves are universally encountered in digital switching circuits and are naturally generated by binary (two-level) logic devices. They are used as timing references or “clock signals“, because their fast transitions are suitable for triggering synchronous logic circuits at precisely determined intervals. However, as the frequency-domain graph above shows, square waves contain a wide range of harmonics; these can generate electromagnetic radiation or pulses of current that interfere with other nearby circuits, causing noise or errors. To avoid this problem in very sensitive circuits such as precision analogue to digital converters, sine waves are used instead of square waves as timing references.

In musical terms, they are often described as sounding hollow, and are therefore used as the basis for wind instrument sounds created using subtractive synthesis.