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