This document provides information about bone conduction hearing. It begins by explaining how normal hearing works through air conduction and the role of the ear drum and cochlea. It then describes how bone conduction works, bypassing the ear drum and transmitting sound vibrations directly to the cochlea through the bones. The document discusses how Ludwig van Beethoven discovered bone conduction and its benefits for people with hearing loss. Potential advantages of bone conduction over air conduction are presented. The document concludes with references.

1. IN THE NAME OF
GOD

2. Reza Barzegar Peraee
Student of the IRIB University
reza.barzegar.1993@gmail.com

3. Subject : Bone Conduction
Lecturer : Reza Barzegar Peraee
Insturctor : Mr. Saffar
Lecture : Basic of Acoustic
November 2016

4. Ear Structure

5. 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 these
sound 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.

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

7. 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.

8. 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.

9. Benefit for people with hearing aid
Most 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.

10. 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.

11. Bone Conduction / Air Conduction Comparison
Bone 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)

12. Traditional Headphone / Bone Conducting Headphone

13. 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, 119-122
4.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 Altuna
7. Wikipedia

14. Imam Ali said :
“God has given to man nothing better than wisdom”
Thank you for your cooperation.
Yours sincerely
Reza Barzegar Peraee
November 2016