(I preface my remarks by pointing out that the Hum may have acoustic prerequisites stemming from many different possible sources, ranging from mining to pipelines to all sorts of large-scale industrial activity. My best guess is that this is the case in Windsor, Ontario, Canada).
The Hum and the big solar flare that’s hitting us now
My best bet right now is that Hum is rooted in very low frequency radio (electromagnetic radiation) transmissions with frequencies between 3 KHz and 30 KHz. It is theorized that frequencies above 16 KHz in particular may be responsible, or at least a prerequisite in many situations. The biophysical side of the model is available on this blog.
I travelled across the western half of Canada this summer, by plane and by train, and everywhere I went I listened late at night. It was air travel for the trip eastward, which disrupted my perception of the Hum. Just as I was nearing my third day in Winnipeg, we headed East to a cabin on a good-sized lake in northwestern Ontario. On about my second or third day there, the Hum returned, lasting up until lunchtime, and if things were quiet and the doors and windows closed, I could notice it during the afternoon. I retrieved my tone generator and matched the frequency right around 56.5 Hz, which is what I hear at home. (I’ve searched the Hum Database and found some folks in New Zealand who perceive the same thing). Train travel back to Vancouver masked the Hum completely (very high level background train noise and semi-random lateral movements). I have returned home on the Sunshine Coast and of course the Hum is still here, and quite loud right now.
So what about the solar flare? I’ve proposed a mechanism to explain the worldwide Hum. Key to that theory is the role of the Earth’s ionosphere in reflecting and carrying radio signals at VLF frequencies. The ionosphere changes height diurnally, seasonally, and randomly. If the Hum is indeed rooted in ionospheric effects, then a big solar flare should cause some big effects. John Beaman was to my knowledge the first person to note some very interesting correlations between solar activity and the frequency of postings to the Yahoo Hum Sufferers. You can find his materials in that forum.
My theory predicts that there should be significant changes in the Hum across the planet. The Hum will appear in places, go quiet in others, and will strengthen in some locations. Perhaps the next time a really big flare comes at us, we can get organized enough to document things in real time, which might provide important evidence.
Meantime I’ll watch the reports pouring in to the Hum Database to see if there are spikes in new reports during the present solar episode.