1 / 12

The Lever Ratio

The Lever Ratio. Purpose of ME. To transmit sound energy from the air space in the EAC to the fluid in the cochlea This is accomplished by vibration of the ossicles. So what if we didn’t have a TM or any ossicles?. 99.9% of sound waves would bounce off the oval window

serina-dillon
Download Presentation

The Lever Ratio

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Lever Ratio

  2. Purpose of ME • To transmit sound energy from the air space in the EAC to the fluid in the cochlea • This is accomplished by vibration of the ossicles

  3. So what if we didn’t have a TM or any ossicles? • 99.9% of sound waves would bounce off the oval window • This energy reflected off oval window gives about a 30 dB hearing loss • Purpose of the TM and the ossicles -- eliminate IMPEDANCE MISMATCH • IMPEDANCE – the resistance to flow of energy

  4. Two Forms of Impedance • Resistance • Reactance • Stiffness • Mass

  5. Area Advantage TM 2 OW 55 mm 2 3.2 mm 55 : 3.2 = 17 : 1

  6. Lever Advantage Malleus is 1.3 times longer than the Incus

  7. Area & Lever Ratio 17 * 1.3 = _______ therefore the overall increase in pressure equals: 20 Log 22 = _________________ 22 to 1 26.84 dB or 27 dB

  8. The Acoustic Reflex

  9. STAPEDIUS vs. TENSOR TYMPANI • 6 mm in length • 25 mm in length • Arises in bony canal • adjoining the facial canal • and inserts on the head • of the stapes • Arises from wall of • Eustachian tube and • inserts on the upper • margin of the • manubrium of malleus • Cranial Nerve VII • Cranial Nerve V • Activates by startle • response and/or tactile • stimulation of the • orbital area • Activates by acoustic • (acoustic reflex) and • nonacoustic means

  10. Neuronal Organization of Acoustic Stapedius Reflexes

  11. Clinical Acoustic-Reflex Protocols • Acoustic-reflex thresholds • AR thresholds vs. auditory thresholds • Reduction of .6 - .7 dB per dB 80 80.3 - 80.4 83 - 84 84.5 - 86 88.4 - 91.2 We only measure up to 110 dB HL

  12. Acoustic Reflex Profiles in Specific Pathologies • Middle ear disorders • Facial nerve disorders • Cochlear disorders • Eighth nerve disorders • Central (Brainstem) disorders

More Related