A requirement to find the source of low-frequency EMF noise led me on a ghost chase – and you may have a similar problem, so here are the details.
The term electrosmog is sometimes used to describe the general pollution (to use a pejorative term on purpose here) of the environment by electromagnetic waves. We’re all familiar with this problem in the unlicensed bands used primarily by Wi-Fi devices; here we just call this interference. But there are all manner of books and devices on the market to help one understand (perhaps another pejorative term, at least in this context; many of these are written by politicians, and amateur ones at that, not engineers) what electromagnetic fields are and why they are harmful to living organisms (really getting pejorative now, aren’t we?).
OK – I need to go on record, again, stating my belief, based on years of study of the issue, that the electromagnetic fields found in consumer environments are harmless, and, yes, this includes emissions, intentional and otherwise, from cell phones, access points, wireless routers, and all manner of ZigBee, Bluetooth, Z-Wave, and on and on. I have seen no evidence that even microwaves, again in the form of what we see in consumer environments, cause any harm at all. This is not to say that all electromagnetic radiation is harmless; that’s most certainly not true. Industrial and military equipment can indeed be deadly in the wrong hands, which is why only the right hands touch them (I hope). Gamma rays and such, which are 100% natural, by the way, are truly deadly, and I personally assume that all ionizing radiation is harmful at any amplitude. But the electromagnetic fields we’re normally exposed to, again, are not going to cause us any problems.
With respect to our health, anyway, but it sure can be irritating regardless. I play (well, sort of) electric guitar in a hobbyist, non-professional mode, although I am developing a product for electric guitars that I’ll likely never discuss here as such would be way off-topic indeed. Anyway, the key to the workings of this instrument is a device called a pickup, which is a transducer that converts the vibrations of metal strings into very-low-level electromagnetic waves, suitable for subsequent amplification. The pickup is usually a passive device that just a coil of wire wrapped many times around a magnet of some form. These thus are very sensitive to electromagnetic fields in the environment.
So I thought that the sound I was hearing recently was pretty trashy, and this wasn’t the result of my affinity for heavy-metal distortion. Rather, it was clear that something in my facility was generating a stray low-frequency field, and the problem thus became how to find and neutralize it. Well, I’ve got a ton (literally) of equipment in here, both intentional radiators like radios and unintentional radiators like, well, a lot of stuff. The first step was to unplug everything, and I did, with the exception of all those APs. They’re mission-critical. Ditto for the UPSes they’re plugged into, the FiOS router, and the Ethernet switch. No change.
OK, then, a more scientific approach was indicated. I purchased (Amazon has great prices on these) an AlphaLabs Trifield 100XE Meter, which detects and measures (within reason; this is an inexpensive and essentially consumer-grade product) electrical, magnetic, and microwave (
But it sure looked like I had one (or perhaps many) here. Walking around with the meter I found several strong EM fields, presumably at 60 Hz., since they mostly were coming from the CFLs (compact fluorescent lights) I have dutifully installed here. But shutting these off and even unplugging them had no effect on the audio quality.
In short, I have yet to identify where the field is coming from, and I will keep after this. In the meantime, and all you electric musicians out there already know this, there is a device called a noise gate that is used in just these situations. This is a magic-hand-on-the-input-volume-control that shuts off when the signal drops to very low levels – as in, when one is not playing. When one is playing, the noise is masked by the signal (sound familiar, radio geeks?), especially if that signal is a loud heavy-metal morass. Voilá, problem solved, for now. But I’m not done yet.
