Module 14: Hearing Vocabulary
14-1: Sound Waves
1) Audition: the sense or act of hearing
2) Frequency: the number of complete wavelengths that pass a point in a given time
3) Pitch: a tone’s experienced highness or lowness; depends on frequency
14-2: The Ear
4) Middle Ear: the chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrums on the cochlea’s oval window
5) Cochlea: a coiled, boney, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses
6) Inner Ear: the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs
14-3: Perceiving Pitch
7) Place Theory: in hearing, the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated
8) Frequency Theory: in hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch
14-5: Hearing Loss
9) Conduction Hearing Loss: hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea
10) Sensorineural Hearing Loss: hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves; also called nerve deafness
14-6: Cochlear Implants
11) Cochlear Implant: a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea Module 14: Hearing Vocabulary
14-1: Sound Waves
- Sounds are jostling molecules in the air that bump into each other
- Sound waves are special touch sensations sensed through vibrations and air and bone conduction
- The ears turn vibrations of air into never impulses that our brain decodes into sounds
- Amplitude determines the volume of sound waves or how loud something is
- Lengths of sound waves determine the frequency
- Frequency determines pitch
- Pitch is measures in decibels
- The absolute threshold for hearing is zero decibels (whispers are 20 decibels and a normal conversation is 60 decibels)
- Anything higher than 85 decibels can cause hearing loss
14-2: The Ear
- To be able to hear, sound waves must go through a mechanical chain reaction process to convert into Neural Activity
1) Sound waves travel through the auditory canal from the outer ear to the eardrum that vibrates the waves.
2) The waves get transmitted through the middle ear through three tiny bones (hammer, anvil, and stirrup) to the cochlea in the middle ear.
From there on, the vibrations vibrate the cochlea’s membrane that makes the fluids in its tube jostle that then ripples the basilar membrane and bends the hair cells that trigger the nerve fibers (auditory nerve). Module 14: Hearing Vocabulary - This mechanical reaction causes hair cells to send neural messages (via thalamus) to the temporal lobe’s auditory cortex.
14-3: Perceiving Pitch
- Two theories have been in place on how we perceive pitch
- Place Theory(high pitch): we hear different pitches because different sound waves trigger activity at different places along the cochlea’s basilar membrane
(the brain can determine a sound’s pitch by recognizing the place on the membrane from which it receive
- Frequency Theory(low pitch): the basilar membrane vibrates with incoming sound waves, triggering neural impulses to the brain at the same rate as the sound waves
- Volley Principle: neural calls can alternate firing in rapid succession, in which they can achieve a combined frequency above 1000 times per second
14-4: Locating Sounds
- The placement of our ears allow us to use stereophonic (3D) hearing
- Two ears are helpful because if a sound is going off, the ear closest to the noise receives the sound slightly sooner than the other one
- Sound waves travel 750 miles per hour
- Ears are 6-inches apart
- Intensity difference and time lag are extremely small `
14-5: Hearing Loss
- Problems with the mechanical system that conducts sound waves to the cochlea cause conduction hearing loss
- Causes: punctured eardrum and inability to vibrate in hammer, anvil, and stirrup
- Damage to the cochlea’s hair cell receptors or their associated nerves can cause sensorineural hearing loss Module 14: Hearing Vocabulary - Causes: occasionally disease, biological changes in heredity, aging, prolonged exposure to ear-splitting noise or music
- Once nerves are destroyed, tissues remain dead
- Hearing aids amplify sounds to stimulate neighboring hair cells
- Digital hearing aids amplify vibrations for high frequencies and compressing soft sounds
- Hair regeneration is possible in sharks and birds. Scientists have found a way to regenerate hair cells in guinea pigs, but not humans yet.
14-6: Cochlear Implants
- Cochlear implants are used to restore hearing for people with nerve deafness
- They translates sounds into electrical signals that convey some information about sound to the brain