Final Report on Project C-50, Continuously Coded TDS, November 1, 1943.Final Report on Project C-55, Telegraphy Applied to TDS Speech Secrecy System, Oct.In spite of the declassification of this report, it has continued to languish in obscurity, although PDF versions are now freely downloadable from the Defense Technical Information Center (DTIC) and-in higher quality-from, along with a number of other relevant reports at DTIC: Joliffe (1942-45) and Haraden Pratt (1944-45), while Vannevar Bush had chaired the NDRC as a whole. In 1960, the office of the United States Secretary of Defense declassified a book-length report called Speech and Facsimile Scrambling and Decoding (1946), originally designated “secret” but then already long since downgraded to “confidential.” It had been the third in a series of summary technical reports covering work done during World War Two by Division 13 of the National Defense Research Committee (NDRC), assigned to investigate electrical communication under the direction of C. The relevant spectrograms aren’t at all difficult to access. But when it comes to hearing scrambled speech of the World War Two era, I’m not sure we have any other options. After all, playing back a spectrogram probably isn’t the best way for us to learn what a bald eagle sounds like. However, we can also listen to historical spectrograms just as we’d listen to historical recordings on audiotape or 78 rpm record, as a straightforward means of actualization or eduction, an approach I call paleospectrophony, or “old-spectrum-sounding.” In my book-and-CD publication Pictures of Sound, I presented sound spectrograms of spoken phrases, the cries of bald eagles, sounds of marine life, and whistlers, but these are all subjects we could just as well have heard elsewhere, and I included them mainly as a proof of concept, to prove that paleospectrophony could recognizably transduce bits of legacy audio. Most past efforts to play spectrograms-ranging from the analog Pattern Playback and Icophone to the digital Photosounder-have foregrounded the analytical decomposition of old sounds or the synthesis of new ones. The way I do it, they need to be digitized (if this hasn’t already been done), cropped, and loaded into additive synthesis software, and time and frequency parameters need to be set. When I say spectrograms are “playable,” I mean that they can be played with a bit of effort, and not that they can be played easily with the click of a button or the drop of a needle. But if it does, I haven’t found it, and the only specimens of scrambled-speech audio available online, such as the ones found here, appear to be far more recent. Presumably such recordings existed at one time, and it’s not at all unlikely that something survives out there somewhere-a record of an intercepted enemy transmission, say, or an audio sample included in the soundtrack of a training film. Meanwhile, I’m not aware of any available non-spectrographic recordings made of scrambled speech during the 1940s or before. However, their top priority was the study of scrambled speech, which they illustrated in print with numerous examples, the goal being to train readers to recognize and diagnose different systems. Its developers clearly took an interest in applying it to other tasks as well, such as making recorded speech and other sounds visibly decipherable. But if we want to hear what the secret speech-scrambling technologies of the Second World War sounded like, spectrograms printed in once-classified government documents may be our best bet.Īs it happens, the sound spectrograph was first developed into workable form as a wartime project specifically for analyzing ciphony, or the encryption and decryption of confidential voice transmissions. ![]() ![]() Most spectrograms represent types of content that are readily accessible in other, more convenient formats. The sound spectrogram is a playable audio format, even though it’s usually meant to be seen and not heard.
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