The Wansdyke & District Forums

Odd one and probably nothing. For a few weeks now, out at night doing the bat surveys, I have been aware of a low hum: very low, more felt than heard, a sort of pressure in the ears. Worst in the small hours, worst when it is still, and it seems to come from no direction, or from the ground itself. I have ruled out my own kit and my own ears as best I can. I know the famous Bristol Hum and the Taos Hum and all that, and I know it is usually traffic, or a pump, or tinnitus, or a generator carrying on a still night. I am a sceptic by trade. But I cannot place this one and it is keeping me up, and the bats, oddly, go quiet in it. Anyone else out at night getting this?

its a pump or a compressor somewhere geoff, they carry for MILES on a still cold night, you wouldnt believe how far. dairy out your way? sewage works? someone running a biomass boiler overnight? low frequency travels and travels and you cant tell where its from, thats the whole problem with it, your ears cant place a long wavelength. nine times out of ten its farm or industrial plant ticking over when the air goes still and flat. not saying it isnt annoying.

I will only say that the still cold nights are when the ground is most awake, in my experience, and that you are right it comes from below and not from a direction. I do not call it a pump. But I would not argue with Geoff, who knows more than I do, only note that the animals going quiet is the part the pump does not explain. A compressor does not hush the bats. Something does, out there, on the still nights, and the bats know it before we feel it.

Doreen, the bats are exactly what nag me, and I say that as the resident sceptic. Animals do not respond to a sewage works. I will keep logging it, time and temperature and where, and see if it has a pattern. Probably I will find the boiler and feel a fool, which would honestly be a relief. I would rather feel a fool than keep lying awake feeling the ground hum. I will report back if it does anything interesting.