[lloeki]

To me the first sample sounded like some subway passing by but when you're still far away yet.

That said, after about 15 to 30s of attentive, continuous listening, it started making me increasingly uneasy, as I perceived the sound as being extremely oppressive and ominous, in a very chthonian way. I'm not going to try to listen to that any longer because I'm half sure that could almost turn into a panic attack of sorts or something. Really unsettling.

The second, fractal one didn't produce that effect unless I turned the volume way up, and even then, not as much.

[aisofteng]

The concept of getting a panic attack in response to listening to some audio is completely foreign to me. Is it normal to have that reaction? It sure seems like it wouldn't be.

[nice_byte]

IIRC there's some evidence that very low-frequency sounds may cause feelings of anxiety and fear in human subjects. Very low frequency sounds may occur prior to catastrophic events like earthquakes, and some animals have been known to react to it. It's plausible that humans have evolved a similar protection mechanism which has gradually atrophied. That being said, I'm talking about sub-20 Hz frequencies here. I don't think these recordings contain that and I don't think it would be possible to reproduce on regular headphones anyway...

[lloeki]

Missing funtamentals are a thing though.

[0]: https://en.wikipedia.org/wiki/Missing_fundamental

[FrozenVoid]

Professional headphones can reach 3hz and subwoofers about 0.5hz.

[lloeki]

Constant, uniform stimuli for extended periods of time can produce weird effects on the mind. Think about stuff like sensory deprivation, staring at oneself in a mirror, anechoic chambers... And if someone can find a given sound soothing it's not out of this world to think that another sound could have the opposite effect.