Register to reply

Vibration Question relating to People

by minger
Tags: people, relating, vibration
Share this thread:
minger
#1
Feb24-05, 01:19 PM
Sci Advisor
P: 1,498
I have a quick question about vibrations. Is there such thing as a natural frequency of the human body? I tried to google some information, but couldn't find anything. The reason for this is that we have a couple of big heat exchangers here at work, and some operators were complaining about noise coming from them. When I got in between them, I could instantly "feel" the sound waves. After taking many vibs measurements, it seemed the frequency was around 100 Hz, with relatively high amplitude. After finishing (which took about an hour), I felt sick to my stomach, and just generally bad.

I was wondering if this was around some kind of natural frequency of humans. I mean, it wasn't just the fact that it was low frequency and loud. I mean, I'm sure at some point, we've all known someone who has huge speakers in their cars, but it wasn't like this. Just kinda curious.
Phys.Org News Partner Engineering news on Phys.org
UConn makes 3-D copies of antique instrument parts
Amazon worker piloted drone around Space Needle
Five next-generation technologies for positioning, navigation and timing
Artman
#2
Feb24-05, 01:26 PM
P: 1,591
Little more information, Minger. What temperatures are they operating at, what are the fluids, and how are they supported?
minger
#3
Feb24-05, 01:36 PM
Sci Advisor
P: 1,498
Why are the heat exchangers important? It could have been any piece of equipment making a constant frequecny vibration, I was just assuming that the reason that it was affecting me was because of the frequency.

But, if you wanna know some info on the exchangers, they are both supported by two "feet." The channel in temperature are super hot, can't make an estimate, but it was uncomfortable to stand close to them. Shell-side, the temperatures aren't too bad, maybe 150F. Fluids are.....gas and water?? I'm not sure, we have a LOT of exchangers here, I'd have to do some research to get the full scoop.

I just asked someone about this, and they said they heard somewhere that Hitler used to employ a similar tactic for his "brainwashing." I think the human low limit for hearing is like 40 Hz, so "supposedly" he used to get big speakers and emit like a 20-30 Hz tone before coming onto stage to get a speech. This made everyone feel sick, but they didn't know why, then when he would come on stage, they would turn the speakers off, and they would feel good again.

Artman
#4
Feb24-05, 01:52 PM
P: 1,591
Vibration Question relating to People

Just curious. I was wondering how the sound was being generated and if temperature could be a contributing factor. Although I agree that vibrations have an effect on humans.
minger
#5
Feb24-05, 01:55 PM
Sci Advisor
P: 1,498
Oh, I believe the sound is just coming from the vibrating machinery. It is rather warm in that area, as the exchangers are pretty hot (at least on one end).
FredGarvin
#6
Feb24-05, 04:20 PM
Sci Advisor
FredGarvin's Avatar
P: 5,095
You know I have heard of this field of study but never really looked into it. I did come across the following in a paper regarding naval aviators:

Effects of Vibration on the Body

A number of factors modify the effects of vibration on humans, including tissue resonance, duration of exposure, individual variations, and other simultaneous environmental stresses. For example, acceleration increases the body's rigidity, reducing its shock-absorbing properties and increasing the transmission of vibration energy to the internal organs (Antipov, Davydov, Verigo, & Svirezhev, 1975). The effects of vibration on the body are determined by the frequency ranges involved.

Effects at less than 2 Hz. Vibrations in the frequency range of 0.1 to 0.7 Hz most often produce motion sickness in humans. Vibrations of 1 to 2 Hz are generally associated with increases in pulmonary ventilation, heart rate, and sweat production above that level considered normal for any other stress present.

Effects from 2 to 12 Hz. Tolerance in this frequency range is usually limited by substernal or subcostal chest pain, with thresholds at approximately 1 to 2 Gz and 2 to 3 Gx. The etiology of the pain is the same for both axes of vibration:displacement of the abdominal and thoracic viscera induces stretching of the chest wall, with torsion at the costochondral junctions of the ribs. Dyspnea is the second most common symptom in this range, apparently with the same etiology as chest pain. Centrally induced hyperventilation can be produced by vibrations around two axes at acceleration amplitudes above 0.5 G in the range of 1 to 10 Hz.

Cardiovascular effects are maximized in Gz+gz (i.e. a Gz-acceleration environment with interposing +gz vibration) at 3 to 6 Hz and in Gx+gx at 6 to 10 Hz. The changes seen are increases in heart rate, arterial blood pressure, central venous pressure, and cardiac output; these are accompanied by a corresponding decrease in peripheral resistance. These changes all resemble nonspecific exercise responses.

Abdominal discomfort and testicular pain are common complaints due to stretching of viscera and force applied to the spermatic cord, respectively.

The headache commonly associated with this frequency range has several explanations. In a Gz+gz environment, the mechanical forces are not well attenuated by the skeletal system. In a Gz+gz environment, the head is forced out of phase with the headrest and repeatedly impacts against it. In Gx+gy environments, the problem is the same only more so; strain, spasm, and soreness of the neck are added to the symptoms.

Finally, bloody stools, transient albuminuria, and transient hematuria are occasionally seen in helicopter pilots flying heavy schedules. Such symptoms are attributed to vibration, and they usually disappear after a few days rest.

Effects above 12 Hz. In these frequencies, there is more concern about effects on performance (vision, speech, fatigue) than about injuries.
The whole paper is here: http://www.iiimef.usmc.mil/medical/F...APTER%202.html


Coming from an ex-Army aviator, I found pretty much what you were wondering about:

NATURAL BODY RESONANCE

Natural body resonance is the mechanical amplification of vibration by the body occurring at specific frequencies. Table 7-2 shows resonant frequencies for various parts of the human body.

http://cavalrypilot.com/fm1-301/tab7-2.gif

Table 7-2. Resonant Frequencies for Various Parts of the Human Body
That paper can be found here: http://cavalrypilot.com/fm1-301/ch7.htm
Cliff_J
#7
Feb24-05, 09:17 PM
Sci Advisor
P: 789
My guess would be that you may have been capturing a harmonic and the fundamental is a subsonic closer to some of the info above. I remember reading about some scientists affected by an imbalanced air handler fan creating subsonics making them sick and the solution was a very low-tech means of rubber isolation mounts.

At that low a frequency and large an amplitude isolation would seem the only solution, stiffening/massloading to shift the spectural balance or absorbtion/diffusion of the airborne waves are completely impractical.

Cliff
minger
#8
Feb25-05, 06:30 AM
Sci Advisor
P: 1,498
Wow, I'm gonna start reading those now, looks like good stuff. Thanks for the info!!
Charlotte Mordin
#9
Jul22-06, 12:52 AM
P: 3
I have come across this thread by searching for subsonics + heart and would like to thank you very much as I was beginning to suspect that I was turning into one of those neurotic middle aged women that you hear about. I would also like to check if there is any advice that you may have for me.

About three months ago I woke in the night with a weird sensation in my abdomen, as of tiny whirlpools. This continued for some time, but progressed to my heart, which increasingly felt as if was racketing around in my chest - since then I have become more and more aware of my circulation and heartbeat at all times. It is really a very unpleasant feeling, right now I feel as if my heart/sternum is in a tight grip.

As far as I can make out this is because the lights on the new football stadium just down the road from me are still on. My experience is that this will lessen once they get turned off by the increasing daylight. Certainly all this started when they were turned on - they are the big red lights that you can see in the picture at the Arsenal site (url at end) which are situated at intervals all round the stadium. These lights emit a penetrating hum at night, which may be amplified by the hollow sounding chamber of the gigantic parking lot underneath the stadium. Until I read your thread I had not associated the tension in my neck with all this, like a pyramid from my shoulder-blades to the back of my head.

They are not going to turn off these lights because I ask them to. Meantime I am seriously concerned for my health. I need to get some kind of proof that they are emitting sub-sonics, and thanks to yourselves I have something to show about the effects. Could you suggest any way that I might be able to find the equipment to do this ?

I do hope that someone picks up this message,

Best Wishes to you all,

Charlotte Mordin

PS As insurance, here are two e-mail addresses: charlotte.mordin@zoom.co.uk or
charlotte_mordin@eu.yr.com






http://www.arsenal.com/emirates.asp?...irates+Stadium

)
FredGarvin
#10
Jul22-06, 07:07 AM
Sci Advisor
FredGarvin's Avatar
P: 5,095
Isn't Arsenal one of the biggest names in soccer in Europe? You do not have an easy road ahead of you. Since you are talking about a well established, professional stadium, you are not going to be the right person to do any kind of study on the effects of these lights. Unless you have credentials in the area of medical vibrations or acoustics, you would not be taken seriously. If this is indeed a problem, then you need to start looking for consultants or colleges that have the people that can do this sort of analysis. Unfortunately, you'll most likely need lawyers too. No corporation is going to spend the kind of money you are talking about without a fight, no matter the reason.
NoTime
#11
Jul22-06, 09:46 AM
Sci Advisor
HW Helper
P: 1,571
Don't know about UK.
In the US it would probably be easy to find a lawyer looking for a potential income source.
Charlotte Mordin
#12
Jul23-06, 11:26 AM
P: 3
I really appreciate your replies - thankyou. Yes, you are right about Arsenal being big. Even so, they do have to comply with the local council - this is a heavily populated area, with three schools in the immediate vicinity and I am reasonably confident that Arsenal would not be allowed to endanger people's health and well-being if it could be proved that this was the case.

I may get somewhere either through my doctor or through the council. It all rests on getting an analysis of the vibrations, via, as suggested, consultants or colleges. From Minger's initial posting I got the idea that this is not all that difficult.

Anyway, I shall push ahead. I think that I may know someone who knows someone in a related area. Thanks again for the helpful observations.

Charlotte
J77
#13
Jul24-06, 03:15 AM
P: 1,157
Quote Quote by FredGarvin
Since you are talking about a well established, professional stadium, you are not going to be the right person to do any kind of study on the effects of these lights.
It's a brand new stadium.
Hawknc
#14
Jul24-06, 04:08 AM
P: 70
Charlotte - certainly low-frequency vibrations can cause effects similar to what you're describing. I'd suggest doing a search for "whole body vibration", since that's more what you're looking at than subsonics per se, and plenty of research has been done in that field regarding the effects of low-frequency vibration on human health. If you could discover what frequency the low-pitch hum is that these lights are emitting, it would certainly help your cause as different frequencies cause different effects in people - for example, 20 to 30 Hz can cause headaches and neck problems, whereas 2.5 to 5 Hz can cause pain in the lumbar region. Chest and abdominal pain, as well as nausea, are common side effects.
Charlotte Mordin
#15
Aug3-06, 02:55 PM
P: 3
Thankyou Hawknc, Fred Garvin and J77

Whole body vibration certainly describes what I have been feeling, and thanks to this clue I have already found a couple of relevant papers.

Recently Arsenal has kept the huge lit-up signs turned off (no doubt people nearer to the stadium have objected) and my symptoms have also calmed down noticeably. However, the generators are still running and hummning all night and I do want to make the point to Arsenal via the Council Planning Commiittee so that at least the lights will stay off and maybe the dynamos insulated in some way.

Definitely frequency analysis is the goal - that would be undeniable proof as it links to established effects (As mentioned I think I know someone that might be able to help but have an outstanding something I have to do for them before I can decently ask). By the way, I have bought a hammock and should get it fixed up this weekend. If the vibration is coming through the floor I figure this should help a lot. Is it possible that the vibration may be ambient, as with regular sound ?

Once more may I say just how much I appeciate being able to link up to this academic forum.

Best Wishes to all,

Charlotte
La La
#16
Aug13-08, 11:37 AM
P: 1
Hi everyone, i wonder if someone can help please...?

I used to work on the first floor of an office block which was a suspended floor over the car park below. The floor used to vibrate (very subtle but definately there all day long). Apparently the floor was known to vibrate because there were too many people on the floor and because of the carpark underneath (and possibly even the air conditioning unit which sat directly below). I sat in the worst area of the floor.

Over time, I began to feel very low and 'not quite right', but more worryingly there were times when i could feel a 'tightening' in my chest and my throat would also tighten. This feeling in my throat would subside when I left the office but never went away and over a few months it got worse until it felt like I had a premanant lump in my throat. I went to a specialist as i was convinced I had cancer, but was given the all clear.

It has never gone away, even though I left this job last September. It gets worse now if I get stressed or if I sit for any length of time in my husbands sports car - despite the fact that he's had this car for years and I never used to suffer from this feeling.

I am convinced it was the vibrations I experienced whilst working in this office - I was there for about 10 months - that has caused whatever this peculiar thing is but have never been able to find out anything about it.

Can anyone help?
yasmine
#17
Oct6-08, 06:09 PM
P: 1
hey
i am a new member in this site but i think that this site will be my favorite site
i want to ask some question about the difference between shaft &bearing vibration
and how did i understand the vibration curve or graph that between vibration or mobility or force with frequency
i mean fundamentals basics
FredGarvin
#18
Oct7-08, 06:49 AM
Sci Advisor
FredGarvin's Avatar
P: 5,095
Welcome Yasmine.

Don't post in an existing thread. Start a new one. Ask away, but please, try to be preceise as possible. It is very difficult to answer questions like "How do you do vibration analysis?"


Register to reply

Related Discussions
Question about vibration General Physics 7
Question relating to time independent perturbation theory Quantum Physics 0
Question on Vibration Mechanical Engineering 0
Question relating to Maths General Discussion 11
Question relating to probablilties General Math 1