Tuning and sensitivity of the human vestibular system to low-frequency vibration

Authors:  Todd, Neil; Rosengren, Sally; and Colebatch, James

55237main_vestibsystemSummary:

  • This study is published in a peer review journal.
  • Reasearchers tested subjects (against a control subject) with a wide range of low frequency noise and infrasound at varying intensities
    The tests showed: ‘that what you can’t hear can harm you”
  • The link to low frequency noise from wind turbines appears to send false signals to the highly sensitive structures within the inner ear (otolith organs & semicircular canals), causing dizziness, vertigo, and nausea, along with cognitive and memory deficits, and anxiety and panic attacks. The latter behavioral symptoms are tied to the inner ear, as Dr. Pierpont’s book explains.
  • This research provides scientific evidence for Dr. Pierpont’s contention regarding the effects of wind turbine noise/vibration on the human vestibular system (i.e., inner ear)
  • An affected vestibular apparatus, is the core of Wind Turbine Syndrome, as Pierpont conjectured in her forthcoming publication.  This article provides substantial evidence that she’s correct.

Abstract. Mechanoreceptive hair cells of the vertebrate inner ear have a remarkable sensitivity to displacement, whether excited by sound, whole-body acceleration or substrate-borne vibration. In response to seismic or substrate-borne vibration, thresholds for vestibular afferent fibre activation have been reported in anamniotes (fish and frogs) in the range −120 to −90 dB re 1g.

In this article, we demonstrate for the first time that the human vestibular system is also extremely sensitive to low-frequency and infrasound vibrations by making use of a new technique for measuring vestibular activation, via the vestibulo-ocular reflex (VOR). We found a highly tuned response to whole-head vibration in the transmastoid plane with a best frequency of about 100 Hz. At the best frequency we obtained VOR responses at intensities of less than −70 dB re 1g, which was 15 dB lower than the threshold of hearing for bone-conducted sound in humans at this frequency. Given the likely synaptic attenuation of the VOR pathway, human receptor sensitivity is probably an order of magnitude lower, thus approaching the seismic sensitivity of the frog ear. These results extend our knowledge of vibration sensitivity of vestibular afferents but also are remarkable as they indicate that the seismic sensitivity of the human vestibular system exceeds that of the cochlea for low frequencies.

Neil P. McAngus Todd
Faculty of Life Science, Jacksons Mill
University of Manchester
Manchester M60 1QD, U.K.
neil.todd@manchester.ac.uk

Sally M. Rosengren
James G. Colebatch

Prince of Wales Clinical School and Medical Research Institute
University of New South Wales
Randwick, Sydney, NSW 2031, Australia

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10 thoughts on “Tuning and sensitivity of the human vestibular system to low-frequency vibration

  1. I am interested in your suggestion that “the seismic sensitivity of the human vestibular system exceeds that of the cochlea for low frequencies”.

    From my surveys I have no doubt that the magnitude of annoyance from low frequency sound is related to a range of measures which have an auto correlation in respect of sounds where the variation in magnitude is modest (i.e. in relation to general environmental sounds e.g. from building vibration).

    These measures are :- (1) Prominence (i.e the differential of the sound magnitude), (2) The Intensity (Integral sum of the product of prominence and magnitude through time) and (3)the differential of Intensity.

    1 and 2 correlate precisely for sounds of a constant magnitude.

    (3) is a useful concept as it is relatively independent of the magnitude of the sound.

    I am convinced that as annoyance is ‘grey’, i.e. contains no tonal quality except for the roughness and magnitude of the sensation, then the nervous system is in some way processing the intensity of the impacting sound. I see no evidence that the ears are involved. Stopping the auditory canal does not alter the annoyance sensation , even in percieved magnitude.

    Vibro-tactile stimuli produce a sensation which is percieved as sound. This interaction is ‘post-perceptual (See paper by Yarrow, Haggard and Rothwell).

    Fluctuations in the ‘Intensity’ of a measured low frequency sound can map as similar pattern to the sensation. The emissions from standing waves in a water hydrant we measured had a pronounced pitch of about 400 ms.

    Somewhere on th ebody the flctuations in Intensity are sensed. This could be large areas of skin/muscle as suggested by the muscle sensations which frequently accompany the annoyance, or any other site.

    Please do you have any special indication that the site is movement in the whole or part of the vestibule??

    The next step in my research is to see if I can detect any correlation between the intensity of the vibro stimulus and the induced pseudo-sound.
    Certainly that sensation is, for me, identical to the annoyance from intense, low-frequency sound.
    (Including wind farm noise and naturallty occurring moorland ‘howling’).
    J.B. 10/03/09.
    Please ,

  2. The sensation induced by ‘Low Fequency Sound’ is a monotone with variations in magnitude and in ‘roughness’ i.e patterns of magnitude fluctuation. There is no sensation similar to pitch alteration and the magnitude of the response appears not to vary with the magnitude of the impacting sound. Magnitudes as low as 0.01 pascals can generate intrusion once sensitisation has occurred and the level of the annoyance sems to relate to the energy input (the Intensity)rather than to the magnitude of the sound.

    From my obsevations the best fit with the level of annoyance is given by the degree of fluctuation in the Intensity of the impacting sound.

    The measure used is the average Intensity over 2 seconds (calculated from 5ms. samples) divided by (the average Magnitude * the average fluctuation rate/second) over the same period.

    A series of two second periods were selected at a site where the annoyance magnitude varied considerably overnight and where the 2 sec. sound magnitudes had Lin Leq levels varying between 0.01 and 0.1 pascals. The above measure fitted the annoyance assessed on a 5 point scale better than any of the other intrusion measures considered.

    What is interesting is that this measure is, in the first degree, independent of both the magnitude and the frequency profile in the sound.

    “The form of the ‘annoyance magnitude measure’ fits with the form of the sensation. It implies that it is the variation in Intensity which gives the degree of the reaction. The independence of this measure from any tonal frequencies in and from the magnitude of the subject sounds is reflected in the qualities in the sensation.”

    Intensity roughness might well be able to predict the degree of annoyance from any measurable sound. Importantly this technique also assesses broad band emissions and those with significant components with frequencies below 10Hz.

    [Measuring the Intensity using 5ms. samples limits the upper frequencies which are captured in the Intensity measure to, say, 100 Hz. Most annoying sounds have key lower frequencies than that, or perhaps equipment will become avilable which is capable of calculating shorter sample periods.]

    That fits with the model that it is the variation in intensity which generates the response and that the response is monotone and similar over a range of sound levels.

    [Note: The comparison of energy levels between samples of differing magnitudes suggests comparing ‘energy roughness’ using physical , rather then logarithmic units.]

    J.Burton.

  3. I have an extreme sensitivity to low frequency sounds and would like to learn more about the effects and how to cope with this sensitivity as it is very, very unnerving (almost maddening) if I can’t get away from it or make it stop. I have asked my ENT about it and he knows nothing about it. I would also be willing to participate in studies regarding this issue.

  4. I am a mom with a child that might have a hypersensitive vestibular system (ex- unusual fear from movement of a swing). We used a big fan in the hallway at our house every nap and nighttime sleeping from the time she was a newborn. Could this possbily have caused harm?

  5. I also struggle with the annoyance of exteme sensitivity to very low frequencies. they drive me nuts, when most others cannot even detect them. what can i do?

  6. I am interested in this thread as I am sensitive to low frequencies coming from industry in my residential area. I’m looking for coping ideas as well as lobbying advice before I approach the brewery which has been here much longer than me.

  7. LORI – Your query has prompted me to send this update on my researches into low frequency sound annoyance. (See my posting of 3.10.2009 ).
    As before I stress that the update content is my opinion relating to several years exposure and research into annoyance.
    I have no formal training in sound measurement or in neurology – but my comments seem to have an internal logic and are consistent with my and other people’s observations.

    I have no doubt that the magnitude of this annoyance is related to the intensity of the impacting sound. Intensity is the rate of supply of energy from the sound and is importantly different from the sound magnitude i.e. sound pressure level.
    Fluctuations in intensity are always accompanied by fluctuations in sound pressure, These pressure fluctuations may or may not have a frequency in the audible range.
    There is an auto-correlation between fluctuations in intensity and those in sound pressure but they are not necessarily in phase. Intensity magnitude is calculated from the cross product of the sound pressure and the rate of change of pressure, i.e. pressure gradient. At low magnitudes the pressure gradient can be the more significant factor in the calculation..

    The response mechanism to this impacting sound seems very likely to be related to the pressure/sound detectors in the skin. Pacinian Corpuscles are one form of skin pressure sensor. These have a recovery period after discharging of about 5 milliseconds.
    Fluctuations in sound intensity, where there is an inter-peak period somewhat longer than this 5 ms., would tend to cause many corpuscles to produce synchronised ‘firing’ of stimuli into the nervous system. Other forms of skin pressure transducers (i.e. sensors) have longer recovery periods.

    I have been subject to annoyance from a known source of emissions for several years. These are caused by structural collisions between my house structure and an adjacent house. These collisions occurred at particular periods and were accompanied by an audible signal at 180-185 Hertz. – i.e. with an inter peak period of 5.6 milliseconds. That is some 10% longer than the assumed Pacinian Corpuscular recovery period.

    I understand that neurologists have traditionally measured the relationship between these corpuscular discharges to the nervous system and the degree of skin displacement. There must also be a relationship with the sound intensity provided that this intensity fluctuates sufficiently to induce a resonant response at the corpuscle. There would/might be no need for the skin surface to be deflected.

    My tests suggest that the somatosensory system response is related to the energy supplied to the skin surface by fluctuations in sound pressure. The energy supply (intensity) appears to cause resonance in the skin transducers. Firing would occur above different fluctuation spacing thresholds for each type of sensing corpuscle.
    For example University of Kentucky research suggests 50 Hertz (i.e. 20 millisecond spacing) for sensors in the lip vermillion.

    So my assumptions are:-
    1. This ‘pseudo-sound’ low frequency sound annoyance cannot be heard by others because it is not sensed through the auditory system.
    2. The somatosensory response to touch is universal – skin movement is felt by all.
    I understand that a vibrotactile response can be induced in every test subject by increasing the magnitude of the stimulus.
    3. It is a reasonable speculation that the resonant response to low frequency fluctuations from sound pressure fluctuations is also universal – i.e. that sensitisation just changes a pre-existing threshold.
    4. The response to sufficiently loud sound energy is also known to be universal – There is research which shows that ‘waking’ is caused by sound of sufficient intensity- whether or not the frequency of that sound lies in the audible range.
    Also some (many?) persons with complete hearing loss are woken by sound of unexceptional intensity.

    In conclusion:

    It looks as though the annoyance induced by low frequency and infrasound is actually a reflection of a series of ‘waking’ stimuli. i.e. The annoyance is repetitive waking.

    (A team at the University of Toronto have demonstrated that a steady state response in the somatosensory cortex can be induced by vibotactile stimuli spaced up to seven seconds apart. Presumably sound intensity peaks produce similar stimuli and would also induce a continuous ‘annoyance’ response.)

    So, LORI :-.

    The Brewery.
    You believe that a brewery is causing your low frequency annoyance. You ask how to demonstrate this?
    The only easy way is to demonstrate a coincidence in timing between your annoyance and some quality in the sound which the brewery plant emits.

    You could try by having a continuous survey made by a sound consultant.
    It may be that there is some audible frequency component which also occurs at the same time as your annoyance. If so the brewers should be able to recognise what part of the plant is involved and, if friendly, they may then investigate. I speculate that part of your home vibrates in resonance with sound or vibrations emitted by the plant circulation pumps or the flue fans.
    If as a commercial organisation they then take a hard line then I am afraid all that you can do is rely on whatever the Canadian guidelines are to prove that they are generating a nuisance.-
    Alternatively you could try a continuous sound level survey taken in a suitable form to be converted into a pattern showing of the low frequency component of the sound’s intensity.
    This might be of little legal use, but it could give you the satisfaction of being able to prove that there is some constituent in the sound emissions which causes or correlates with your annoyance. It is not just in your imagination!

    ‘Coping’ is a difficult area.
    You can reduce the annoyance by reducing the intensity of the sound. You probably know that you sleep better with your radio playing. Masking works.

    There are ‘experts’ who suggest stress management and relaxation techniques. I suspect that they would reduce the annoyance. I have found that they cause one to be distracted from the ‘annoyance’ between intensity peaks rather quicker than would otherwise be the case.

    Our problem here in England is that there is no guideline for the level of the intensity of low frequency sound which is, or is not, acceptable. The lawyers’ precedents suggest that annoyance is allied to tinnitus, and this is currently assumed to be a defect in the subject’s audible sound detection system..
    I know of no published guidance of how annoyance relates to the intensity of low frequency sound or to infrasound emissions.
    We do have a ‘criterion curve’ relating the propensity of low frequency sound (10-160 Hertz) to cause annoyance but it is known that this is not adequate to solve many instances of annoyance.

    The U.K. ‘Health Protection Agency’ recently published a paper ‘Health Effects of Exposure to Ultrasound and Infrasound’ .
    This paper described the sleep disturbance and other health effects resulting from annoyance.
    It dismissed ‘ Cutaneous Perception’ as a possible source for the stimulus which induces annoyance. That opinion ( see paragraph 2.3.1.2) depends upon the assumption that the impacting sound energy cannot be detected without significant skin deflection.
    I doubt that assumption. Modest deflection could be sufficient to induce resonance in the corpuscle structure to the point of discharge.

    If you do carry out a sound survey then I suggest that you get your expert to contact me.

    John Burton.

    P.S. If I am correct then also :-

    1. I suspect that the annoyance produced by wind turbines might well be reduced by introducing a ‘rough’ reflecting surface onto the mounting columns.
    2. Every one of my low frequency noise survey sites in urban areas have shown emissions related to the pumped water distribution network.
    Water distribution is usually pumped with fluctuations at or below 50 Hertz. (i.e. with peaks further apart than 20 milliseconds). Smoothing these and/or changing the pump construction to increase fluctuation frequency considerably should reduce annoyance. (This seems likely to be the cause of the widespread Bristol and Auckland ‘hums’ ).
    I suspect that this change would also reduce the distribution network’s energy consumption.

  8. I would like responses please in respect of any other sites where the intensity pattern has been researched ( rather than the SPL)- If the intensity fluctuations are spaced sufficiently far apart for skin transponders to have recovered between peaks then simultaneous ‘firing’ of the corpuscles is to be expected. Has anyone else found acute ILFN reactions from fluctuations of the order of 180 -200 Hertz?
    J.B.

  9. I live in Humboldt County in Northcoastal California. We are about 2 miles uphill from a power plant. It feels to me like there is an 18-wheeler truck idling a couple of houses down. The vibration is similar to the washing machine when it is in the spin cycle. It vibrates my whole body and a feel nauseous. Other people I talk to aren’t bothered by it at all. Even with earplugs in at night, my body still senses the oscillation and whirring. I don’t know what to do other than to move. Perhaps I need to try to mask it with a radio or a white-noise machine. Any advise or suggestions would be greatly appreciated.

  10. Patty: Earplugs will not affect your response reaction to the impacting vibrations as they are probably being sensed by your skin, not by your ears. If others cannot hear the disturbances then neither can you. The touch/position sensors in the skin are an alternative mechanism for sensing the incoming energy from physical vibrations and from air vibrations(sound).

    Try turning off your water supply at the main and running off a little water ( and some hot water to de-pressure your pipework.) This should silence your water tank vibrations and the consequential noise and vibration from your house(?) structure. You might then be able to sleep without any trouble.
    If that works consider converting your hot water system to a ‘header tank and gravity feed’ arrangement.

    My research on other sites suggests that the majority are influenced by the energy delivered by the pumped fluctuations in the water mains. This can be by direct impact on the contained water in your pressurised hot water system but other annoyance is associated with standing vibrations in static water lines either closed end mains or fire hydrants. These can cause ground vibrations and hence vibrations in the structure of your dwelling.

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