I think a lot of people missed a BIG fact here. The OP said that he was talking about rolled speech inversion. This in not encryption and can be unscrambled very easy. See this WIKI . -Edit For anyone who is wondering "scrambling" is different from Encryption in two major ways. The first is that it is not legal for anyone to Decrypt a signal for which they are not the intended recipient. This does not apply to a scrambled signal. The second is the way that the two systems work. A scrambled system/channel simply applies filters to the audio to make it hard to understand and in most cases it can be un done with a small effort. Encryption uses a crypto to encode digital audio data. A private key is stored in the transmitter and in the receiver that allows for the process to take place.
You're picking nits here. As far as RadioReference (and the law) is concerned, if the purpose is to hide the content of a transmission from unauthorized listeners, it's encryption. And as I noted earlier, we do not track encryption type, only the fact that it is there.