Hearing, Ear, and Sound

sound

when object in the world vibrate, they transmit acoustic energy through surrounding medium in the form of a wave

Main task of the ear

measure sound and transmit it to the brain

Main task of the brain:

interpret the signal, and use it to figure out what is out there in the world

Psychoacoustics

study of psychological perception of the physical dimensions of acoustics (branch of psychophysics)

Frequency

# of cycles per second

amplitude

amount of pressure displacement

Pinna

collects sounds, funnel them into ear canal

Tympanic membrane (eardrum)

thin sheet of skin that vibrates in response to sound, Protect middle ear (ex: from water and bacteria)

Ear canal

protect tympanic membrane (ear drum)

parts of outer ear

pina, tympanic membrane, ear canal

Ossicles

3 smallest bones in the human body, size of letters on a page

parts of middle ear

ossicles, ear canal, hammer, anvil, stirrup, oval window, cochlea

function of middle ear

transmits the eardrum’s vibrations to the oval window, which transmits them to the fluid filled cochlea

Oval window

flexible opening to the cochlea through which the stapes transmits vibration to the fluid inside

Cochlea

fluid filled, spiral structure of inner ear contain the organ of Corti

Middle Ear Acoustic Reflex

Eardrum and stirrup bond (part of ossicles) are each equipped with tiny muscles that contract in the presence of loud sounds, Muscle contraction stiffens the eardrum and restricts the movement of the ossicles, thereby damping the vibrations passed to the inner ear

parts of the inner ear

Semicircular canals, vestibular nerve, auditory nerve, cochlea

Semicircular canals

vestibular systems

Auditory nerve

collection of neurons that convey info from hair cells in the cochlea to the brain stems (afferent neurons) and from the brainstem to the hair cells (efferent neurons)

Cochlea basic idea

vibrations at oval window cause basilar membrane to wiggle

wiggles in cochlea trigger

voltage channels in hair cells in organ of corti

Vestibular canal

one of three fluid filled passages in the cochlea. Extends from the oval window at the base of the cochlea to the helicotrema at the apex

Stapes

most interior of the three ossicles. Connected to the incus on one end, the stapes presses against the oval window of the cochlea on the other end

Round window

soft area of tissue at the based of the tympanic canal that releases excess pressure remaining from extremely intense sounds

Basilar membrane

plate of fibers that forms the base of the cochlear partition and separate the middle and tympanic canals in the cochlea