IN THE NAME OF

GOD

Reza Barzegar Peraee

Student of the IRIB University

reza.barzegar.1993@gmail.com

Subject : Bone ConductionLecturer : Reza Barzegar PeraeeInsturctor : Mr. SaffarLecture : Basic of AcousticNovember 2016

Ear Structure

How we Hear?Normal sound waves are actually tiny vibrations in the air.The vibrations travel through the air to our ear drums.The ear drums in turn vibrate, decoding thesesound waves into a different type of vibrations that are received by the Cochlea, also known as the inner ear.The Cochlea is connected to our auditory nerve ,which transmits the sounds to our brain.

How we Hear with Bone Conduction?Bone Conduction bypasses the eardrums.In bone conduction listening, the bone conductiondevices ( such as headphones ) perform the role of your ear drums.These devices decode sound waves and convert them into vibrations that can be received directlyby the Cochlea, so the ear drum is never involved. The “sound” reach the ears as vibration throughthe bones (or skull ) and skin.

History :Ludwig van Beethoven, the famous 18th

century composer who was almost completely deaf, discovered Bone Conduction.Beethoven found a way to hear the sound of the piano and clenching it in his teeth.He received perception of the sound when vibrations transfer from the piano to his jaw.This has proven that sound could reach our auditory system throw another medium besides eardrums and the other medium is our bones.

Why Bone Conduction?Listening with enhanced bone conduction is:1. a way of receiving more vibratory input than through ordinary listening, both through osseous and non-osseous pathways.2. a means of tuning in to how we first listen.3. a means of stimulating the inner ear without directly involving the middle ear.4. more stimulating to the vestibular apparatus than is air conduction listening.5. an opportunity to stimulate the vestibular system, particularly the saccule (a receptor for vertically oriented gravitational), with extra input to facilitate grounding, verticality, basics of body awareness.6. a gateway for additional influence of sound on CNS system.7. a way of helping tune the individual in to the mechanism of sound conduction used in vocal production.8. helpful in integrating high frequencies.9. a way of facilitating inner listening.10. often found to facilitate the process of change.

Benefit for people with hearing aidMost cases of hearing loss are due to damages to the eardrums. Since bone condition does not use the eardrum. People with hearing difficulties would be able to hear clearly again with bone conduction, provided that their cochlea is in healthy and normal condition.

The result of the bone conduction using :These figures show the mean hearing gain obtained at each of the frequencies under study. The first audiogram (Fig. a) reflects the pre-operative situation, where the difference between AC and BC is evident. The second audiogram (Fig. b) reflects the results at one month, and the third (Fig. c) the results at one-year follow-up, where we can see almost complete resolution of the ABG(air-bone gap), without observing a significant variation of BC.

Bone Conduction / Air Conduction ComparisonBone Conduction• internal and external vibration• faster conduction speed than AC• tunes in from 10Hz → ultrasonic (up to 100KHz) range (Nishimura et al, 2002;Hakanssan et al., 1996)• bilateral cochlear stimulation secondary to vibration (Stenfelt, 2002)

Air Conduction• external vibration

• 20 – 20K Hz range; ultrasonic inaudible

• unilateral cochlear stimulation(Stenfelt, 2002)

Traditional Headphone / Bone Conducting Headphone

References :1.Allen, G., Fernandez C. (1960). The mechanism of bone conduction. Annals of Otology, Rhinology and Laryngology 69, 5-28.2.Sheykholeslami, K. et al. (2001). Frequency sensitivity range of the saccule to bone conducted stimuli measured by vestibular evoked myogenic potentials. Hearing Research 160, 58-62.3.Nishimura, T. et al. (2002). Effect of stimulus duration for bone-conducted ultrasound on N1m in man. Neuroscience Letters 327, 119-1224.Arnold A, Fawzy T, Böhnke F. Investigation of bone conduction thresholds in otosclerosis. ORL J Otorhinolarngol Related Spec. 2007;1:269---74.5.Carhart R. Clinical application of bone conduction audiometry. Arch Otolaryngol. 1950;51:798---808.6.Study of the Improvement in Bone Conductionn threshold After Stapedectomy by Leire García-Iza, ∗ Juan José Navarro, Miren Goiburu, Nuria Pérez, Xabier Altuna7. Wikipedia

Imam Ali said :

“God has given to man nothing better than wisdom”

Thank you for your cooperation.

Yours sincerely

Reza Barzegar Peraee

November 2016