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Low-frequency noise A biophysical phenomenon

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). 1 of 16. Contents. Sources low-frequency sound

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Low-frequency noise A biophysical phenomenon

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  1. Low-frequency noiseA biophysical phenomenon Dr Mireille Oud medical physicist / consultant (Congress “Sound, Vibrations, Air quality, Field & Building”, 6 November 2012, Nieuwegein, The Netherlands) 1 of 16

  2. Contents • Sources low-frequency sound • Biophysics perceptibility(neurobiologist A.N. Salt, Washington University) • Health effects • Conclusions • Advices • References 2 of 16

  3. Sources low-frequency sound (<<150 Hz) Via air: up to 1 km • Wind turbines • Gas transport • District heating • Industry • Difference tones • … (Ref.: Kohlhase 2011) Via ground: up to 100 km  cumulation sources 3 of 16

  4. Sources low-frequency sound Wind turbines Gas grid (Ref.: Kennisportal Wind energy) (Source.: www.gasunie.nl) 4 of 16

  5. Biophysics perceptibility Organ of balance ______  ___  Cochlea (Ref.: Chittka & Brockmann 2005) (Ref.: Prasad) 5 of 16

  6. Biophysics perceptibility __________ Cochlea (Ref.: Encyclopaedia Brit. 1997) (Ref.: Madhero88) • Outer hair cells: pre-amplifier • Inner hair cells: to brain 6 of 16

  7. Biophysics perceptibility test animal test animal (Ref.: Salt 2011) • Can become • audible • Audible for every-one (Ref.: Pedersen 2008) 7 of 16

  8. Biophysics 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

  9. Biophysics perceptibility response cochlea test animal • Audible cochlea-activity (500 Hz) interacts with inaudible cochlea-activity (5 Hz)low tone audible through amplitude modulation 5 Hz 500 Hz audible 5 Hz (Ref.: Salt & Lichtenhan 2011) 9 of 16

  10. Biophysics 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  (Click here, in presenting mode of powerpoint. Use head phone.) (Source: M. Oud 2012) 10 of 16

  11. Biophysics perceptibility G-weighting: ISO 7196:1995 (Ref.: Cedric 2004) weighted wind-turbine spectra (Ref.: Van den Berg 2006) •  dBC and dBG more realistic 11 of 16

  12. Health 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

  13. Health 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

  14. Conclusions • 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

  15. Advices • 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

  16. Referenties • 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 frequencieswith 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 16 of 16

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