is it possible to create infrasound simply by vibrating a string???

Feb 2020
1
0
russia
ok this lad vibrated his string with 5hz,11hz,22hz... but i dont feel intuitively that it was the infrasound.
first of all, heavier a string- lower should be the frequency, is his rope thick and heavy ? NO. And various articles about infrasound simply babble about earthquakes. And do those vibrations transfer to the clamp that is holding the string?

Secondly, when elephants communicate with infrasound, i suspect they radiate normal frequency MODULATED by the infrasound.

Discuss infrasound in solid bodies here.
 

topsquark

Forum Staff
Apr 2008
3,056
651
On the dance floor, baby!
The video is simply describing resonance vibrations on a string. It doesn't appear to reference anything to infrasounds. But if the speaker is eminating sound waves at 11 Hz then, yes, it is in the infrasound range so there really isn't any room for doubt. An infrasound frequency is simply a low frequency sound wave.

I have no idea how elephants communicate.

-Dan
 
Jun 2016
1,304
628
England
If we start with sound, it is simply a variation in the spacing between the molecules of the medium it is travelling through.
Note the travelling through, the undisturbed molecules will maintain an even spacing relative to each other.
If they are forced closer together, or further apart then (when released) they will move back toward their original balance point.
However this movement will push and pull on their neighboring molecules, creating a sound "wave" which will move through the material.
Infra sound is just sound waves that are of a lower frequency than our ears are sensitive to, ultra sound is sound of a higher frequency than our ears are sensitive to.
Varies from person to person, but around 40hz to 20000hz.

Watching natural history documentaries of Elephants you can hear that they are constantly making very low rumbling vocalizations.
Analysis of these sounds has shown that what we hear are just the higher frequency part of these vocalizations, and that they include lower frequencies we can't hear (infra sound)
It is unclear how much information is contained within these vocalizations beyond, I am here, and general mood indicators.

Infra sound has the advantage that it can travel greater distances and is less affected by obstacles than higher frequency sounds.
Thus one herd of elephants can be well aware of the presence and crucially the mood of a neighboring herd many miles away.

The infra sound generated in the video would be very quiet.
 
  • Like
Reactions: topsquark
Apr 2015
1,159
305
Somerset, England
OK let's start with some facts and figures.

Sound travels at 1100 feet per second in air, and the human range of hearing is normally reckoned to be 20Hz to 20,000hz in the young and 20Hz to 12,000hz in the old.
Humans start to feel sound rather than hear it at frequencies below 20hz. So this is the beginning of infrasound.
Sound at 7hz is dangerous because it is the frequency at which internal organs start to resonate.

The basic relationship is speed = frequency times wavelength
so a I hz wave has a wavelength of 1100 feet and a 10hz wave a length of 110 feet.
So your rope needs to be at least half a wavelength long to transmit significant power at the fundamental.
The ropes in the video show multiple nodes and are not vibrating at the fundamental, despite the activator frequency.
They will be vibrating at an overtone or harmonic.
Such systems do not input a large part of their power to the air at the fundamental.
This is why bass speakers aremuch less efficient than high frequency ones and need to be much larger.

So the short answer to your question is
Yes a rope can generate infrasound if it is
a) Taught enough
b) Long enough
 
  • Like
Reactions: topsquark