Voice inversion
（重定向自Speech inversion）
Voice Inversion scrambling is an analog method of obscuring the content of a transmission. It is sometimes used in public service radio, automobile racing, cordless telephones and the Family Radio Service. Without a descrambler, the transmission makes the speaker "sound like Donald Duck". It is called "voice inversion", but the technique operates on the passband of the information and so can be applied to any information being transmitted.