I was eight, maybe nine, when I first heard it. At first I didn't think anything of it: the parental units were still awake and probably watching TV, and I didn't like going in there and facing them while they were concentrating on the screen. What's more, some of the stuff they watched actively creeped me out: there was a CBS detective series called Checkmate, which ran for two seasons in the early Sixties and which had, to my mind anyway, the grossest-looking opening credits in the history of television, although the theme song, very early John Williams, had a certain verve to it. Not that I knew anything about verve in those days. Or, for that matter, John Williams.

But I was definitely hearing voices, and it wasn't their voices, so I assumed it was the TV — until I rolled over in bed and the voices abruptly stopped. That's strange, I thought, and moved back to my original position. The voices resumed, choppy and distorted, but clearly recognizable as human, if not necessarily as television stars. I had no idea what was going on, but at the time I was not inclined to lose any sleep over it.

After several recurrences over the next few weeks, I was becoming ever so slightly panicky: who were these people, and why were they talking in my room? Could anyone else hear this? And how did they know I was moving around to get away from them?

Finally I figured something out: every time I heard them, the room fan — we didn't have things like air conditioning in those days — was running at medium speed. Didn't explain where the voices came from, exactly, but it gave me some meager amount of control over the matter, and for the moment, that was enough. What I didn't expect is that I'd be hearing the same sort of chopped-up voices at irregular intervals for the next fifty years, and that I'd still be puzzling over them.

In 2005, I wrote this:

A sound: loudest at first, then softer, then softer still, then finally gone. In technical terms, the wave diminishes in amplitude until eventually it's lost, faded into the background noise, indistinguishable from any other random quantity of air.

My father has always believed, perhaps with a nod to Zeno, that "finally gone" is never finally achieved, that under the right set of circumstances, or with the right set of tools, that sound can be reclaimed, amplified, restored to its original loudness: it never really went away to begin with.

And I wouldn't have entertained such a notion, I suspect, had it not been for those mysterious voices from the far corner of the room, set in motion at however many RPM and seemingly just waiting for me to not quite fall asleep.

Now of course the sound of a voice does not imply someone speaking at that very moment; I understood phonographs, and how they could reproduce a sound that had been produced long before. What I did not understand is how the not-quite-random rotation of the blade in a cheap box fan could create a vibration that sounded so much like a voice, or like several voices. I wanted to believe it was radio, plucked out of the very sky and turned into sound, but radio occasionally served up music, if only in the form of a jingle, and these voices never had any musical accompaniment of any sort.

A brief wade into unexplained-mysteries.com yielded up one explanation:

Electrical fans when they are on are always humming a low-pitch noise and you may receive a strange musical sound or spoken conversation out of nowhere ("Ugh...I'm must be crazy, the voices in my head"). The technological advancements like radios (esp. the AM frequency) and your PC on idle mode, are sensitive to receive very low-decibel sounds not normally heard by human ears. That does require scientific investigation and inquiry on how these mechanical devices seemingly act like antenas.

Yeah, okay. I picked up a 50,000-watt radio station in the wires to a 56k modem in the dear, dead dial-up days. But that was easily recognizable as radio, and the source was easily determined. (What's more, repositioning the wires would usually — not always — quiet it down.) And if these sounds are so low in frequency that they can't be heard, what the hell am I hearing? Specific harmonics that happen to fall in the human vocal range? Any frequency has harmonics; but the higher-order harmonics tend to be at lower amplitudes.

But then, farther along in that same thread:

There may be a mundane explanation for some/most/all of it... You may be surprised to know that power companies use the power supply to 'talk' to some devices on the grid! Your local situation may vary, but here where I live every thirty minutes on the hour and half hour (and sometimes at other intervals) they send a series of 'ripple signals' at ~1050Hz into the electricity supply grid. These signals, also known here as "Audio Frequency Load Control (AFLC)" are used to switch various automated devices that change tariffs and perform other tasks on demand — eg hot water services and other devices that they may wish to turn on/off to control the load... Problem is, these signals are audible in many devices (like ceiling fans and other motorised devices) and things which contain noisy transformers or sensitive electronics. It doesn't hurt them, but it can be annoying. Some power supply companies may prefer you didn't know about this, because they would rather you don't go chasing them to find out how to fix something that they are causing. You can get filters to stop it, but they can be expensive, and in most cases it is only a minor annoyance..

As they often send several sequences of signals at varying intervals and lengths, it can indeed sound just like muted voices... I hear it most days/nights (hot climate, ceiling fans) and sorta like it... it's quite soothing if you don't think of it in a sinister way...

Hmmm. Assuming A=440, 1050 Hz is approximately the C two octaves above middle C, so it's certainly within one's hearing range. I've got only one problem with this explanation. From Wikipedia:

The general control algorithm for [load-frequency control] was developed by N. Cohn in 1971.

By which time I'd already been hearing these things for nearly a decade. Then again, that's an algorithm; it wouldn't necessarily apply in cases where a fixed frequency is in use, since there'd be nothing to calculate.

Maybe I should just sleep on it — or try to, anyway.

The Vent

  24 March 2015

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