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Low-frequency noise A biophysical phenomenon

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Presentation on theme: "Low-frequency noise A biophysical phenomenon"— Presentation transcript:

1 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

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.: 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 5 Hz Audible cochlea-activity (500 Hz) interacts with inaudible cochlea-activity (5 Hz)  low tone audible through amplitude modulation 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 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 Why is low-frequency sound experienced as nuisance?
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: Dr Mireille Oud: Prof. A.N. Salt: ISO norm dBG: ( and (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: /journal.pbio Encyclopaedia Britannica (1997) “Cochlea” Kennisportal Wind energy on land (2011), “Bestaande windparken”, Min. Infrastructuur and Environment e.a. Kohlhase S (2011), “Explaining buried pipeline induced LFN hum and gas turbine flutter …” Brookfield Ct, USA Madhero88: OpenLearn Labspace, “Hearing – section 3.3 The role of the basilar membrane in sound reception” 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. Salt A.N. (2011), “Processes underlying homeostasis of cochlear fluids”, Washington univ. 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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