Sounds of the '60s
An electrical dawn chorus of whistles and chirps.
There was a VLF receiver design in Practical Wireless (UK) sometime in the '60s for tuning in to this. Required a very long aerial and to be about a quarter mile from any main electricity wiring. I was intending to build one, but radio control equipment proved more tempting.
It looks like someone has been tuning in on that frequency with some modern gear. Nice to hear what it actually sounds like!
(Suitable '60s icon? Or was the TV series Whacko with headmaster Jimmy Edwards in the late '50s? I was quite amazed to find it on here. No helpful links to retirement homes required just yet thank you☺)