Hacker News Reader

Comment by 1970-01-01 | Hacker News Reader

1970-01-01

"Undetectable" is false. At 20Hz, you cross over from hearing sound to feeling it. I think earthquakes are sub-20Hz.

I agree that overall the word choice is poor/ambiguous.

But I think grammatically "undetectable" modifies "sound" here, which is true if the physical stimulus is not detectable as sound, but tactile.

Is it really sound if it is undetectable as such? Isn't sound our reaction to a pressure wave (in a certain range over which we have 'hearing')?

Generally you say you "feel" those low frequencies not "hear" them.

But I get what you're saying, what is sound exactly? Is it something that is perceived in our eardrum, or is it something beyond that?

Well animals can hear sounds at frequencies that we can't, so the cutoff shouldn't be when we can detect something. But in that case, do we set a cutoff on the lowest/highest frequencies that we know some animal can hear? Then we might discover something later that increases the range, what do we do then? It just makes more sense to generalize sound past what's actually audible, in my opinion at least.

Then would you consider radio waves to be "light"?

(I was implicitly including other animals, some of which can hear sounds outside the human range, even if they cannot participate in online conversations.)

Exactly. It's not sound, it's infrasound. "Sound" means audible to humans, much how "light" means visible to humans (e.g. radio waves are not considered "light").

I couldn't find if this is the case in the paper but unless they created a pure tone at 20Hz (i.e. a sine wave oscillating at 20Hz) any sound will have higher harmonics. Even though the fundamental is 20Hz, it'll also sound 40Hz, 60Hz, 80Hz (in decreasing volumes) etc and these higher harmonics can or will be audible. Besides, especially in Western classical music, when we use double bass at very low frequencies, it's not always meant to be audible, it's sometimes meant to create a physical effect i.e. feel it through your skin/body instead of your ear, similar to percussion in some settings.

> Some VLFs were above the predicted perceptual thresholds, although consciously undetectable. Because VLFs were relatively near thresholds (that were determined in silence) whereas non-VLFs were far above thresholds (see supplemental material), we believe that auditory masking of the VLFs contributed to their being undetectable.

>we believe that auditory masking of the VLFs contributed to their being undetectable.

Not good enough for science.

https://en.wikipedia.org/wiki/Auditory_masking is pretty well established scientifically.

That's for audible sound! One can't just assume it applies to inaudible frequencies.

> To confirm that the VLFs were not consciously detectable, 17 new participants (one of whom participated in the concert experiment) completed a two-alternative forced choice task using the same VLF speakers in the LIVELab. On each trial, participants heard two pairs of 3.5 s excerpts from the concert audio and indicated which pair’s excerpts were different (all excerpts in the trial were identical except for the presence or absence of VLFs in one excerpt). Participants performed at chance (mean 49.8% correct, SD = 4.56%), and a Bayesian t test on participants’ rates of correct responses indicated substantial evidence for the null hypothesis — that participants could not detect the presence/absence of VLFs (n = 17; prior = Cauchy distribution centred on 0 with width = 0.707; BF0+ = 4.36; Figure 1F).

Do I have to quote the whole article for you to read it?

If deeply wide low frequency waves are detectable as we both agree, that would genuinely explain why the horses and wildlife fled the area around the Mt. St. Helens eruption with seemingly uncanny head start. Enough of a mass run that it was observed and noted. Just like here in North Texas when big prairie thunderclaps can rattle just about everything in a brick house set solidly on a foundation.

My Raspberry "Shake & Boom" has an infrasound sensor.

https://shop.raspberryshake.org/product/turnkey-iot-atmosphe...

Yes, the correct word is "inaudible".

Anyone who's ever been to a live music event can attest to "detecting" sound <20Hz without their ears. And it's pretty obvious how feeling the sound in your body, especially the percussive elements, would encourage dancing.

Inaudible? Mentioned higher up, or lower, I can't always tell on HN.

Reply on news.ycombinator.com