Ankur Desai

A lot of people will be familiar with ultrasound, which is at the very top of our hearing.

We can't hear it, but of course, if you blow a dog whistle, that's ultrasonic.

We can't hear it, but a dog can hear it.

Way at the bottom of our hearing spectrum is infrasound, and it's only if it's incredibly loud could you then actually hear it.

There's obviously a natural source for it that can come from thunder and volcanoes, but in our modern world, there are man-made sources of it, and that includes...

old pipes, boilers, ventilation systems, air conditioning units, anything like that, basically.

Now, you said earlier that it's also the context where you're hearing these infrared sounds.

Absolutely.

There's this idea of psychological priming.

So if you walk into a big cathedral, for example, there's an expectation of the sort of experience you might have.

If you walk into a spooky looking, you know, dilapidated haunted house, there's an expectation.

So you're primed to have a sort of experience.

Now, in both of those different environments, you can be exposed to infrasound, but your interpretation of what's happening to you will vary.

parapsychologist Kieran O'Keefe there.

And if this is the type of thing you're into, Kieran is a regular contributor to the podcast Uncanny, which is available wherever you get your BBC podcasts from.

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