Sound and auditory mechanics. impact loud speaker upon particle distribution in the air

sound and auditory mechanics

impact loud speaker upon particle distribution in the air

sound amplitude depends on variation of sound pressure

modulation of atmospheric pressure = 100.000 Pascal

peff = (½ √2) pmax

hearing threshold = 0.00002 Pa

SPL (dB) = 20×log (p/pref)

reference 2.10-5 Pa

pref, 0 dB SPL

SPL = 20×log (p/pref)

when you double sound pressure, sound intensity increases with ?

when you double sound pressure, sound intensity increases with 6 dB

20 log p1/p2 = 20 log 2 = 20×0.3 = 6

Question

When two students talk non-synchroneously with a sound intensity of 60 dB SPL each, what do they produce together ?

Answer

When two students talk non-synchroneously with a sound intensity of 60 dB SPL each, they produce together 2 times more energy = 63 dB total

when you double sound pressure, sound intensity increases with 6 dB

20 log p1/p2 = 20 log 2 = 20×0.3 = 6

but energy increases with 3 dB

10 log e1/e2 = 10 log 2 = 10×0.3 = 3

Question

When two students talk synchroneously with a sound intensity of 60 dB SPL each, what do they produce together ?

Answer

When two students talk synchroneously with a sound intensity of 60 dB SPL each, they produce together 66 dB total

Question

What is the total sound intensity in a room with- A radio 70 dB SPL- Two students speaking asynchronous, each 60 dBSPL- one plane flying over with 80 dB SPL perceived in the room

Question

What is the total sound intensity in a room with- A radio 70 dB SPL- Two students speaking asynchronous, each 60 dBSPL- one plane with 80 dB SPL

First transfer into energies, then sum and transfer in dB again.Result = 80.1 dB

sound intensity decreases with r²

 Normal hearing threshold 1000Hz  0 dB SPL

 Falling leaves  10 dB SPL

 Whispering  20 dB SPL

 Very soft talking in a room  40 dB SPL

 Normal speact 1at 1 m  60 dB SPL

 Loud conservation with shouting  80 dB SPL

 Pneumatic hammer  100 dB SPL

 Disco  110 dB SPL

 Very loud sound speaker  120 dB SPL

 Starting airplane at 20 m.  130 à 140 dB SPL

 Pain threshold  130 à 140 dB SPL

resonance and impedance

auditory canal = open pipe

(1, 3, 5 enz.) x ¼

27 mm = ¼

(1, 3, 5 enz.) x ¼

27 mm = ¼

= 108 mm f = 3100 Hz

gehoorgang = open orgelpijp

resonantiegebied = 2000- 5000 Hz

transition air - liquid

acoustic impedance Z = p / u (in Rayleigh like Ohm)

p: pressure neededu: velocity

impedance endolympfe 56000impedance air = 410

factor 135: 97% reflection: therefore ossicles

resonance including ossicular chain: 1000 Hz

impedance

1. resistence: frequency independent transfer sound energy in heat

2. stifness= elasticity that decreases with frequency

3. inertia increases with frequency

compliance (in ml) = 1 / impedance

Hefboomwerking Middenoor

17x

1.3x 2x

17x1.3x2=44.2 pressure gain

10 log(44.22) = 33 dB theoretical gain

measured: ≤ 30 dB

function inner ear

- mechanical-electricial transition by the inner hair cells

- frequency analysis by macromechanics of the basilar membrane

- increasing sensitivity by micro-mechanics by the outer hair cells

Cochlear model

Ovale venster

Ronde venster

Helicotrema (verbindingScala vestibuli en Scalatympani)

http://www.iurc.montp.inserm.fr/cric/audition/start.htm

- mechanical-electricial transition by the inner hair cells tip link – Hudspeth spring model

- increasing sensitivity by micro-mechanics by the outer hair cells: the cochlear amplifier

- deflecion towards kinociulim decreases receptor potential results in: mechanical deformation of the cortical latticeleading to a shortening in cell body length and increase in diameter

moving the basilary membrane further away from the kinocilium

Mechanics outer hair cells + membrane: second resonator and cochlear amplifier

Animation : http://cc.usu.edu/~dgsinex/courses/SHS311_notes/2-ear/corti.htm

Efferent innervation: function selective hearing

Micro mechanics adds energy to the tranverse wave