Low-frequency noise
A biophysical phenomenon
Dr Mireille Oud
medical physicist / consultant
(Congress “Sound, Vibrations, Air quality, Field & Building”, 6 November 2012, Nieuwegein, The Netherlands)
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Contents
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Sources low-frequency sound
Biophysics perceptibility
(neurobiologist A.N. Salt, Washington University)
Health effects
Conclusions
Advices
References
Sources low-frequency sound (<<150 Hz)
Via air: up to 1 km
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Wind turbines
Gas transport
District heating
Industry
Difference tones
…
(Ref.: Kohlhase 2011)
Via ground: up to 100 km  cumulation sources
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Sources low-frequency sound
Wind turbines
(Ref.: Kennisportal Wind energy)
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Gas grid
(Source.: www.gasunie.nl)
Biophysics perceptibility
Organ of balance
______ 
___
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Cochlea
(Ref.: Chittka & Brockmann 2005)
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(Ref.: Prasad)
Biophysics perceptibility
__________
Cochlea
(Ref.: Encyclopaedia Brit. 1997)
(Ref.: Madhero88)
Outer hair cells: pre-amplifier
 Inner hair cells: to brain
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Biophysics perceptibility
(Ref.: Salt 2011)
Can
become
audible
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Audible
for everyone
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(Ref.: Pedersen 2008)
Biophysics perceptibility
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Occlusion helicotrema
 20dB increase sensitivity
for low frequencies
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(Ref.: OpenLearn LabSpace)
Endolymfatic hydrops
(swelling middle tube)
 dizziness
(Ref.: Salt & Lichtenhan 2012)
Biophysics perceptibility
response cochlea test animal
5 Hz
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500 Hz
Audible cochlea-activity
(500 Hz) interacts with
inaudible cochlea-activity
(5 Hz)
 low tone audible through
amplitude modulation
audible 5 Hz
(Ref.: Salt & Lichtenhan 2011)
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Biophysics perceptibility
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a. mono 220 Hz
b. mono 222 Hz
c. mono 220 + 222 Hz
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d. stereo: left 220, right 222
(Click here, in presenting
mode of powerpoint.
Use head phone.)
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(Source: M. Oud 2012)
Low frequencies audible
for everyone:
beat, difference tone
Superposition of nearly
equal, audible, tones (a
and b)
this amplitude modulation
can be acoustic (c) and
neural (d)
(Useful application: tuning
musical instrument)
Biophysics perceptibility
G-weighting: ISO 7196:1995 weighted wind-turbine spectra
(Ref.: Van den Berg 2006)
(Ref.: Cedric 2004)
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 dBC and dBG more realistic
Health effects
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Still more people perceive LFN (hearing / feeling)
Health effects LFN:
• Dizziness
• Continuous, pulsing pressure on head
• Disturbed sleep
• Stress
• Raised blood pressure
• Heart rhythm disorders
•…
Health effects
Why is low-frequency sound experienced as nuisance?
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Directionless, lacks spaciality  seems “within the head”
Character (monotonous or pulsing) & duration
Lack of autonomy (uncontrollable):
ear plugs no effect: entrance is via bone conduction
Affects physiology (structure cochlea)
Conclusions
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Perception low-frequency sound been demonstrated
objectively (audiograms)
Perception low-frequency sound biophysically explicable
Significant part NL-population experiences damage
Low-frequency sound requires different way of
assessment:
minimally dBC instead of dBA , preference dBG
Advices
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Systematic investigation health issues
More scientific research (medicine & physics)
Defining measurement and assessment methodology
Formulate norms for low-frequency sound
International approach
Makes sources low-frequency restricted
Adjustment home environment?
Referenties
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Dutch low-frequency noise vigilance group: www.laagfrequentgeluid.nl
Dr Mireille Oud: http://nl.linkedin.com/in/MireilleOud
Prof. A.N. Salt: http://tiny.cc/AlecSalt
ISO norm dBG: http://tiny.cc/ISO1 (ISO.org) and http://tiny.cc/ISO2 (DiracDelta science eng. enclyclopedia)
Berg, G.P. van den (2006), “The sound of high winds: the effect of atmospheric stability on wind turbine sound and
microphone noise” Ph.D. thesis, Biomed. eng. dept. Rijksuniversiteit Groningen
Cedric R. (2004), “Ecoaccess guideline for the assessment of low frequency noise“, Proc. of Acoustics 2004, 619–
624, Gold Coast, Australia
Chittka L, Brockmann A (2005) Perception Space – The Final Frontier. PLoS Biol 3(4): e137.
doi:10.1371/journal.pbio.0030137
Encyclopaedia Britannica (1997) “Cochlea” www.britannica.com
Kennisportal Wind energy on land (2011), “Bestaande windparken”, Min. Infrastructuur and Environment e.a.
www.w-i-n-d.nl/
Kohlhase S (2011), “Explaining buried pipeline induced LFN hum and gas turbine flutter …” Brookfield Ct, USA
Madhero88: http://commons.wikimedia.org/wiki/User:Madhero88
OpenLearn Labspace, “Hearing – section 3.3 The role of the basilar membrane in sound reception”
http://labspace.open.ac.uk/mod/resource/view.php?id=415643
Pedersen C.S. (2008), “Human hearing at low frequencies with focus on noise complaints”, Ph.D. thesis, Acoustics
dept. of elec. systems, Aalborg University, Denmark
Prasad, “Mechanical cochlea”, senior design project, Stevens Inst. Techn.
http://mechanicalcochlea.wordpress.com/home/the-cochlea/
Salt A.N. (2011), “Processes underlying homeostasis of cochlear fluids”, Washington univ.
http://oto2.wustl.edu/cochlea/WTPicton_salt_final.pdf
Salt, A.N. & Lichtenhan J.T. (2011), “ Responses of the inner ear to infrasound”, 4th Int. meeting on wind turbine
noise, Rome
Salt, A.N. & Lichtenhan J.T. (2012), “Perception-based protection from low-frequency sounds may not be enough”,
inter.noise 2012 New York