Process of Hearing

1. Topic:
Process of Hearing
Presented by: GROUP 2
Afsara Kafeel
Asiya Omama Bano
Ayesha
Dilkash Firoz
Farheen Ali

2. Process of Hearing
• A Masterpiece of biomedical engineering
• The Ear & the Auditory or neural pathway.
•Hearing Physiology

5. ◼ There are three parts of the ear that work together
to perceive noise:
1) the inner ear,
2) the middle ear,
3) the outer ear.
▪ Each section is composed of structures that
play distinct roles in the process of converting
sound waves into signals
that go to the brain.
Hearing Stages

6. ◼ The outer ear is the first port of call,
i. Pinna- outermost, visible structure of
the ear. The pinna harnesses &
amplifies sounds around 400 hz;
protects ear from damage
ii. Ear Canal- a cylindrical tube which
acts as a narrow passageway leading to
the eardrum; acts like a horn -
amplifies sound ( 3000 hz).
iii. Eardrum- or ‘tympanic membrane’,
the incoming sound waves cause the
eardrum to vibrate; pressure waves are
converted into mechanical motion.
Outer Ear

7. Sound waves, which are really vibrations in the air around us, are
❖collected by the pinna on each side of our head,
❖funnelled into the ear canals and passed onto the eardrum
❖these sound waves make the eardrum vibrate
❖This is where the process of understanding these sound waves begins.
The eardrum is so sensitive to sound vibrations in the ear canal that it can detect even the faintest
sound as well as replicating even the most complex of sound vibration patterns.
Functions of Outer Ear

8. Middle ear
► It is a space between tympanic membrane and the
inner ear (opens via Eustachian tube into
nasopharynx).
► Composed of:-
► The tympanic membrane
► The ossicles:- the malleus,the Incus , the stapes
(connected to the oval window )
► 3 Muscles:- 1 tensor tympani
2 stapedius
► Oval window
► Round window
► Eustachian tube

9. FunctionS of Middle Ear
► Tympanic membrane:- Tympanic membrane (Eardrum)
and ossicles, conduct sound from the tympanic membrane
through the middle ear to cochlea (the inner ear).
► The ossicles:- 3 ear bones amplify sound vibration and
passed that vibration to oval window.
► Oval window:- Transmits sound vibration to inner ear.
► Round window:- releases pressure from sound waves.
► 3 muscles:- Tensor tympani and stapedius muscles
contract reflexly in response to constant loud sound
FUNCTIONS OF THE EAR.
► Eustachian tube:- equalises pressure on both side of
eardrum

10. ► In the absence of the ossicular system and tympanic Membrane Sound waves can still
travel directly through the air of middle ear and enter the cochlea at the oval window.
However, the sensitivity for hearing is 15 to 20 decibels less than for ossicular transmission
► Sound waves vibrate the tympanic membrane.
Tympanic membrane moves the handle of malleus
Incus moves
Stapes move in & out of the oval window.
► The pressure transmitted through cochlea cause stimulation of hair cells in the organ of
corti, which stimulate the auditory nerve.
FunctionS of Middle Ear

11. ●Inner Ear

12. Functions of Inner Ear
►Vibrations from the stapes push on the oval window,
►and set up pressure waves in the fluid-filled cochlea,
►the snail-shaped inner ear that contains the organ of
Corti.
►In the organ of Corti, vibrations are finally transformed
into electrical energy by cells known as hair cells
(stereocilia).

14. ►These hair cells translate the vibrations from sound waves
into electrical impulses that then travel along a complex
pathway of nerve fibers to the brain.
►Once sound is converted to electrical signals in the
cochlea, these signals travel via a complex circuit of
auditory nerve pathways to the auditory cortex and
other parts of the brain that regulate awareness and
sensory perception.

15. Central Auditory Pathway
► This section deals with the structure and function of the Central Auditory Nervous
system (CANS) / Central Auditory Pathway
► Within the brainstem, almost all fibres of the auditory nerve synapse on the cells of
the Cochlear Nucleus.
► The relationship between the cochlear nucleus and higher auditory centers is very
complex.
► Once the electrical signals leave the cochlear nucleus, most of the axons of the cochlear
nucleus cells cross over to the opposite side (contralateral side) of the brain.
► Most of the auditory information processed by each half of the brain comes from the ear on
the other side of the head. Information processed by left brain hemisphere comes from
right ear and that for right brain hemisphere comes from the left ear.

16. ► Both crossed and uncrossed fibres
from the cochlear nuclei synapse in
the area of the brainstem called
the Superior Olivary Complex.
► This is the first place in the
(Afferent) Ascending Pathway to
receive information from both the
ears.
► Neural impulses are transmitted from
the superior olivary complex to
the Inferior Colliculus through
and/or around the Lateral
Lemniscus (some fibres synapse in
the lateral lemniscus but most travel
through it to the inferior colliculus).

17. Auditory Cortex
► After that they travel to the Medial Geniculate Body (MGB) and finally to
the Auditory Cortex. The location of the auditory cortex on the surface of the
brain is where we finally interpret the sound.
► The auditory cortices sort, process, interpret
information about the sound.
► The comparison and analysis of all the signals
that reach the brain enable you to detect certain
sounds and suppress other sounds as ‘background
noise’.

18. To conclude, the sound we
hear proceeds through