The Case of the Telltale Tone

According to technical experts consulted by TIME, the 18 minutes of steady tone overriding conversation on a presidential recording raises the possibility that the noise was introduced during an attempt to erase or re-record on that portion of the tape.

Prime authority for that hypothesis is a Government electronics expert and "wireman" who has carried out bugging and tapping operations for a federal agency. Familiar with the White House recording equipment, he told TIME that the tone could not have been accidentally picked up on the tape while it was being played back for listening or transcribing. Nor, he said, is it likely that the tone, or hum, was recorded during the original taping, since it did not blanket all of the conversation. For a partial malfunction, a plug, or electrical connection, would have to cut out accidentally and just as accidentally resume normal operation after an 18-minute lapse.

That is certainly possible, but this expert found it hard to believe. Rather, he suggested, the hum sounds like "what happens frequently when amateurs try to tinker with a tape." The most likely circumstance, he contended, is that "the hum was recorded when someone attempted to record over the original conversation or tried to erase it." While that was under way, the hum could have been picked up from nearby cords carrying alternating current, such as those to a desk lamp, according to this expert.

Other technical experts consulted by TIME confirmed that the description of the noise suggested a typical 60-cycle A.C. hum,* which is not uncommon in unprofessional recording.

The White House used relatively small (11 by 10 by 4 in.) Sony Model 800B recorders for taping conversations in the Oval Office and the President's Executive Office Building hideaway. On such equipment it takes a malfunction, most commonly in a microphone cable, to pick up an A.C. hum, explains Irving Teibel, president of New York's Syntonic Research Inc. "This is quite common in portable recorders," he adds, but usually affects an entire tape.

Another expert, Mortimer Goldberg, technical operations supervisor for CBS Radio, says that such a malfunction on an original recording would not create an overriding steady tone. "I've been working with tape recorders for 23 years and I've never heard the audio completely replaced by a solid tone," he reports. This would happen only during a rerecording, he says. Such a tone could be deliberately created with an audio signal generator (a device used to inject a desired tone to test or adjust audio circuits), but this could be easily distinguished, he explains, from the sound generated inadvertently from fluorescent lights or an electrical cord. Thus it would be a foolish way to make the conversation unintelligible. Re-recording a new conversation or erasing would be more feasible.

* Normal U.S. house current alternates at 60 cycles, which is an audible frequency. It can be radiated through adjacent unshielded wires, resulting in a hum when one of the wires is related to an audio amplifier circuit.

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