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sound and auditory mechanics

sound and auditory mechanics. i mpact loud speaker upon particle distribution in the air. sound amplitude depends on variation of sound pressure modulation of atmospheric pressure = 100.000 Pascal. p eff = (½ √2) p max hearing threshold = 0.00002 Pa

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sound and auditory mechanics

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  1. sound and auditory mechanics

  2. impact loud speaker uponparticle distribution in the air

  3. sound amplitude dependsonvariation of sound pressure modulation of atmosphericpressure = 100.000 Pascal

  4. peff = (½ √2) pmax hearing threshold = 0.00002 Pa SPL (dB) = 20×log (p/pref)

  5. reference 2.10-5 Pa pref, 0 dB SPL SPL = 20×log (p/pref)

  6. whenyou double sound pressure, sound intensityincreaseswith ?

  7. whenyou double sound pressure, sound intensityincreaseswith 6 dB 20 log p1/p2 = 20 log 2 = 20×0.3 = 6

  8. Question Whentwostudents talk non-synchroneouslywith a sound intensity of 60 dB SPL each, what do theyproducetogether ?

  9. Answer Whentwostudents talk non-synchroneouslywith a sound intensity of 60 dB SPL each, theyproducetogether 2 times more energy = 63 dB total whenyou double sound pressure, sound intensityincreaseswith 6 dB 20 log p1/p2 = 20 log 2 = 20×0.3 = 6 butenergyincreaseswith 3 dB 10 log e1/e2= 10 log 2 = 10×0.3 = 3

  10. Question Whentwostudents talk synchroneouslywith a sound intensity of 60 dB SPL each, what do theyproducetogether ?

  11. Answer Whentwostudents talk synchroneouslywith a sound intensity of 60 dB SPL each, theyproducetogether 66 dB total

  12. Question • What is the total sound intensity in a room with • A radio 70 dB SPL • Twostudentsspeakingasynchronous, each 60 dBSPL • oneplaneflying over with 80 dB SPL perceived in the room

  13. Question • What is the total sound intensity in a room with • A radio 70 dB SPL • Twostudentsspeakingasynchronous, each 60 dBSPL • oneplanewith 80 dB SPL • First transfer intoenergies, thensum and transfer in dB again. • Result = 80.1 dB

  14. sound intensity decreases with r²

  15. resonance and impedance

  16. auditorycanal = open pipe (1, 3, 5 enz.) x ¼ 27 mm = ¼

  17. gehoorgang = open orgelpijp (1, 3, 5 enz.) x ¼ 27 mm = ¼ = 108 mm f = 3100 Hz resonantiegebied = 2000- 5000 Hz

  18. transition air - liquid acousticimpedance Z = p / u (in Rayleighlike Ohm) p: pressureneeded u: velocity impedanceendolympfe 56000 impedance air = 410 factor 135: 97% reflection: thereforeossicles resonanceincludingossicularchain: 1000 Hz

  19. impedance resistence: frequency independent transfer sound energy in heat stifness= elasticitythatdecreaseswithfrequency inertiaincreaseswithfrequency compliance (in ml) = 1 / impedance

  20. Hefboomwerking Middenoor 17x 2x 1.3x

  21. 17x1.3x2=44.2 pressure gain 10 log(44.22) = 33 dB theoretical gain measured: ≤ 30 dB

  22. function inner ear • mechanical-electricialtransitionby the inner haircells • frequencyanalysisbymacromechanics of the basilarmembrane • increasingsensitivitybymicro-mechanicsby the outerhaircells

  23. Helicotrema (verbinding Scala vestibuli en Scala tympani) Cochlear model Ovale venster http://www.iurc.montp.inserm.fr/cric/audition/start.htm Ronde venster

  24. mechanical-electricialtransitionby the inner haircells • tip link – Hudspeth spring model

  25. increasingsensitivitybymicro-mechanicsby the outerhaircells: • the cochlearamplifier

  26. defleciontowardskinociulimdecreases receptor potentialresults in: • mechanicaldeformation of the corticallattice • leading to a shortening in cell body length and increase in diameter moving the basilarymembranefurtherawayfrom the kinocilium

  27. Mechanicsouterhaircells + membrane: second resonator and cochlearamplifier Animation :http://cc.usu.edu/~dgsinex/courses/SHS311_notes/2-ear/corti.htm Efferent innervation: function selective hearing

  28. Micro mechanicsaddsenergy to the tranverse wave

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