TheCodeBreakers
300 to 3,300 c.p.s. It is this frequency band that is inverted. A voice tone
of 300 c.p.s. will emerge from the inverter at 3,300 c.p.s., and vice versa.
A tone of 750 c.p.s. will become 2,250 c.p.s., and again vice versa. It is
the equivalent of a = z,
b = Y.....z = A, a phonetic atbash. Inverted speech
sounds like a thin high-pitched squawking, ringing with bell-like
chimes. The word company resembles CRINKAN-OPE, Chicago, SIKAYBEE.
The inversion pivots in the middle of the frequency band, which means
that tones in this area somersault through a narrow range. A frequency
of 1,625 will become 1,675. This relative lack of change results in the
phenomenon that the word inverter itself, which is composed largely of
such tones, emerges from the enciphering process that it describes
almost unchanged!
Another simple technique is the band-shift. This is a kind of
annaabi.ee 
