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Comment by S_A_P | Hacker News Reader

I think there is another thing that bothers me about infrasonic being “too low to hear”.

It’s not true. It’s grossly oversimplified. I could generate a 1hz signal that I can hear. It’s not the same as something at 400hz but it’s clearly audible with proper sound equipment.

Now as that relates to tornadoes I live in a state where there are occasional tornadoes. Every time one has been close you hear the approach.

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What do you mean that it is audible with proper equipment. The definition of an audible frequency is that you can hear it with your ear and the generally accepted minimum frequency for the human ear to hear is 20hz. Lower frequencies might be detectable by vibration in the body but not by the ear.

If you are using sound equipment then you are instrumentally detecting an inaudible frequency.

Am I misunderstanding?

20Hz and 20KHz are just general guidelines for where sensitivity rapidly falls to zero in people with normal hearing. A lot of (primarily young) people can hear frequencies outside that range. I can still hear a sine wave down to about 14Hz, and I'm not sure if the limit is from my ears or the audio interface that's only rated down to 20Hz.

I can imagine "feeling" 1Hz from a big subwoofer, but it's hard to imagine what actually hearing 1Hz would be like. I wouldn't rule it out, though.

You're sure you're not hearing some harmonic? IIRC THD at lower frequency increases drastically. Or wind noise of the subs (they're moving lots of air)?

You can check with a measurement mic what's audible (& make sure to take measurements at multiple points in space due to the low wave length).

To decrease the lower frequency of the audio interface, you probably have to modify the output DC decoupling capacitors (those act as a high pass; bigger C = lower f).

You can't hear it with your ears but you can feel it with your body (if its strong enough).

I believe I did misunderstand. After re-reading I realized the poster could have meant that lower frequencies may be detectable if _produced_ by proper sound equipment, rather than that they are detectable by the proper sound equipment.

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