Low-frequency noiseLow-frequency noiseA biophysical phenomenonA biophysical phenomenonLow-frequency noiseLow-frequency noiseA biophysical phenomenonA biophysical phenomenon

Dr Mireille Oudmedical physicist / consultant

(Congress “Sound, Vibrations, Air quality, Field & Building”, 6 November 2012, Nieuwegein, The Netherlands)

1 of 16

ContentsContentsContentsContents

Sources low-frequency sound Biophysics perceptibility

(neurobiologist A.N. Salt, Washington University)

Health effects Conclusions Advices References

2 of 16

Via air: up to 1 km

Sources low-frequency sound (<<150 Hz)Sources low-frequency sound (<<150 Hz)Sources low-frequency sound (<<150 Hz)Sources low-frequency sound (<<150 Hz)

Via ground: up to 100 km cumulation sources

Wind turbines Gas transport District heating Industry Difference

tones …

(Ref.: Kohlhase 2011)

3 of 16

Sources low-frequency soundSources low-frequency soundSources low-frequency soundSources low-frequency sound

Wind turbines

Gas grid(Ref.: Kennisportal Wind energy)

(Source.: www.gasunie.nl)4 of 16

Biophysics perceptibilityBiophysics perceptibilityBiophysics perceptibilityBiophysics perceptibility

Cochlea

___

______ Organ of balance

(Ref.: Prasad)(Ref.: Chittka & Brockmann 2005)

5 of 16

Biophysics perceptibilityBiophysics perceptibilityBiophysics perceptibilityBiophysics perceptibility

Cochlea__________

Outer hair cells: pre-amplifier Inner hair cells: to brain

(Ref.: Madhero88)(Ref.: Encyclopaedia Brit. 1997)

6 of 16

Biophysics perceptibilityBiophysics perceptibilityBiophysics perceptibilityBiophysics perceptibility

test animaltest animal

Can become audible

Audible for every-one

(Ref.: Pedersen 2008)

(Ref.: Salt 2011)

7 of 16

Biophysics perceptibilityBiophysics perceptibilityBiophysics perceptibilityBiophysics perceptibility

Occlusion helicotrema 20dB increase sensitivity for low frequencies

Endolymfatic hydrops

(swelling middle tube) dizziness

(Ref.: OpenLearn LabSpace) (Ref.: Salt & Lichtenhan 2012)8 of 16

Biophysics perceptibilityBiophysics perceptibilityBiophysics perceptibilityBiophysics perceptibility

Audible cochlea-activity (500 Hz) interacts with inaudible cochlea-activity (5 Hz)

low tone audible through amplitude modulation

response cochlea test animal

audible 5 Hz

5 Hz

500 Hz

(Ref.: Salt & Lichtenhan 2011)9 of 16

Biophysics perceptibilityBiophysics perceptibilityBiophysics perceptibilityBiophysics perceptibility 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)

a. mono 220 Hz

b. mono 222 Hz

c. mono 220 + 222 Hz

d. stereo: left 220, right 222(Source: M. Oud 2012)

(Click here, in presentingmode of powerpoint.Use head phone.)

10 of 16

Biophysics perceptibilityBiophysics perceptibilityBiophysics perceptibilityBiophysics perceptibility

G-weighting: ISO 7196:1995(Ref.: Cedric 2004)

dBC and dBG more realistic

weighted wind-turbine spectra(Ref.: Van den Berg 2006)

11 of 16

Health effectsHealth effectsHealth effectsHealth effects

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• …

12 of 16

Health effectsHealth effectsHealth effectsHealth effects

Why is low-frequency sound experienced as nuisance?

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)

13 of 16

ConclusionsConclusionsConclusionsConclusions

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

14 of 16

AdvicesAdvicesAdvicesAdvices

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?

15 of 16

ReferentiesReferentiesReferentiesReferenties 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 York16 of 16