Task 7 Good vibrations Flashcards
Fourier analysis
- Method to show level of frequency
* A combination of tones form a complex sound
Rare fraction
back and forth movement of the pressure change, molecules go back and forth
Amplitude or intensity
The magnitude of displacement (increase or decrease) of a sound pressure wave. Amplitude is perceived as loudness
Frequency
For sound, the number of times per second that a pattern of pressure change repeats. Frequency is perceived as pitch
Hertz (Hz)
A unit of measure for frequency. One hertz equals one cycle per second
Decibel (dB)
A unit of measure for the physical intensity of sound. Decibels define the difference between two sounds as the ratio between two sound pressures. Each 10:1 sound pressure equals 20 dB and a 100:1 ratio equals 40 dB
o An increase of 6 dB correspond to a doubling of the amount of pressure
Sine wave or pure tone
The wave form for which variations as a function of time is a sine function
Spectrum
A representation of the relative energy (intensity) present at each frequency
Harmonic spectrum
A complex sound which is a multiple (40, 80, 120) of the fundamental frequency (often caused by instruments)
Fundamental frequency
The lowest-frequency component of a complex sound
Fundamental missing
we would still hear the fundamental frequency when its nit present
Outer ear
the external sound gathering portion of the ear consisting of the pinna and the ear canal
Pinna
the outer, funnel-like part of the ear, sounds are collected from the environment
Ear canal
: the canal which receives bundled vibrations from the pinna and conducts them to the tympanic membrane and prevents damage to the tympanic membrane
Tympanic membrane
Ear drum, a thin sheet of skin at the end of the outer ear canal. The tympanic membrane vibrates in response to sound
Middle ear
An air-filled chamber containing the middle bones or ossicles. The middle ear conveys and amplifies vibration from tympanic membrane to the oval window
Ossicle
Three tiny bones that amplify sound waves
Malleus: Receives input from the tympanic membrane and is attached to the incus
Incus: connecting malleus and stapes
Stapes: Connected to the incus on one end and, the stapes presses against the oval window of the cochlea on the other end
Oval window
The flexible opening to the cochlea through which the stapes transmits vibration to the fluid inside. Border between middle and inner ear
Tensor tympani
The muscle attached to the malleus, tensing the tensor tympani decreases vibration
Stapedius
The muscle attached to the stapes tensing the stapedius decreases vibration
Inner ear
A hollow cavity in the temporal bone of the skull and the structure within this cavity: The cochlea and the semi-circular canals of the vestibular systems
Cochlea
A spiral structure of the inner ear containing the organ of Corti, is filled with water like fluid in the three parallel canals
Tympanic canal: One of the three flud filled passages in the cochlea. The tympanic canal extends from the round window at the base of the helicotrema at the apex
Vestibular canal: extends from the oval window at the base of the cochlea to the helicotrema at the apex
Middle canal: The middle canal is sandwiched between the tympanic and vestibular canals and contains the cochlear partition
Helicotrema
The opening that connects the tympanic and vestibular canals at the apex of the cochlea
Reissner’s membrane
separating the vestibular and middle canals (oval window)
Basilar membrane
forms the base of the cochlear partition and separates the middle and the tympanic canals (made of stiff fibers)
Cochlear partition
the combined basilar, tectorial membrane and organ of corti which are together responsible for the transduction of sound waves into neural signals
Round window
a soft area of tissue at the base of the tympanic canal that releases excess pressure remaining from intense sounds
Organ of corti
is composed of dendrites of auditory nerve fibers and hair cells
Hair cells
Any cell that has stereocilia for transducing mechanical movemtn in the inner ear into neuronal activity sent to the brain; some hair cells also receive inputs from the brain
• Are arranged in four rows that run down the length of basilar membrane one row of about 3500 inner hair cells and three rows with a total of about 10500 outer hair cells
• Stereocilium: Any of the hairlike extensions on the tips of hair cells in the cochlea that, when flexed, initiate the release of neurotransmitter, the shorter ones are in the front and the longer ones in the back
Tectorial membrane
a gelatinous structure, attached on one end, that extends into the middle canal of the ear, floating above inner ear cells and touching outer hair cells
Tip link
A tiny filament that stretches from the tip of a stereocilium to the side of its neighbour
• Mechanoelectrical transduction (MET): When a stereocilium deflects the Tip link pulls on the taller one in a way that opens ion pores and cause depolarisation
Auditory nerve
A collection of neurons that convey information from hair cells in the cochlea to and from the brain stem
Afferent fiber
A neuron that carries sensory information to the central nervous system, are connected to inner hair cells (90% in inner hair cells)
Efferent fibers
A neuron that carries information from the central nervous system to the periphery, connected to outer hair cells, by being stiffer outer hair cells make the cochlea more sensitive and more sharply tuned to particular frequencies
Low-spontaneous fiber
a auditory nerve fiber that has a low rate (less than 10 spikes per second) of spontaneous firing, they require relatively intense sound before they will a higher rates
High-spontaneous fiber
an auditory nerve fiber that has a high rate (more than 30 spikes per second) of spontaneous firing rate, they increase their firing rate to relatively low levels of sound
Mid-spontaneous fiber
An auditory nerve fiber that has a medium rate (10-30 spikes per second) of spontaneous firing. Their characteristics are intermediate between low and high spontaneous fibers
Phase locking
: Firing of a single neuron at one distinct point in the period (cycle) of sound wave at given frequency (neuron need not fire on every cycle, but each firing will occur at the same point in the cycle) above 5000 Hz calculation are not reliable any more
Place code
Tuning of different parts of the cochlea to different frequencies, in which information about the particular frequency on an incoming sound wave is closed by the place along the cochlear partition that has the greatest mechanical displacement. The cochlea narrows and selecting frequencies by this
Characteristic frequency (CF)
The frequency to which a particular auditory nerve fiber is most sensitive
Neural frequency tuning curve
Maps different frequencies along cochlea to measure sound level needed to cause neuron to increase firing
Cranial nerve VIII
is known as the auditory nerve
Cochlear nucleus
the first brain stem nucleus at which afferent auditory nerve fibers synapse
Primary central auditory pathway: (SONIC MG)
o Superior olive: An early brain stem region in the auditory pathway where inputs from both ears converge, displys accurate time .
o Inferior colliculus: A midbrain nucleus in the auditory pathway which receives mostly contralateral input from both ears
o Medial geniculate nucleus: The part of the thalamus that relays auditory signals to the temporal cortex and receives input from the auditory cortex
Tonotopic organisation
A arrangement in which neurons that respond to different frequencies are organized anatomically in order of frequency
Primary auditory cortex (A1
o Core area: gets activated by simple tones
o Belt area: A region of cortex (A1) with inputs from A1, where neurons respond to more complex characteristics of sound
o Parabelt area: A region of the cortex lateral and adjacent to the belt area where neurons respond to more complex sounds as well as to input from other senses
Hearing aid
• Hearing aids amplify sounds higher and keeps them between the new threshold and 100 db so the hearing is squeezed
Electronic ears
Cochlear implants are tiny flexible coils with about two dozen miniature electrode contacts along their length. They put them through the round window as far towards the apex of the cochlea as possible. These stimuluate the corresponding parts what in turn stimulates the corresponding parts of the auditory nerve fibers
Auditory brainstem implant
a prosthesis consisting of a microelectrode that directly stimulates one of auditory processing centers of brainstem and might restore hearing to patients with no auditory nerve or lesions beyond cochlea.
Conductive hearing loss
Hearing loss caused by problems with the bones of the middle ear
o Otitis media: inflammation of the middle ear comely I children as a result of infection, causes conductive hearing loss
Osteosclerosis
Abnormal growth of the middle-ear bones that cause hearing loss
o Can be treated by surgery
Presbycusis
Hearing loss greatest at high frequencies, caused by hair cell damage resulting from cumulative effects over time of noise exposure, ingestion of drugs that damage hair cells, and age-related degeneration
Hidden hearing loss
– Does not normally affect person’s ability to hear sounds, but it makes it harder to hear sounds when there is background noise. Nerve cells are damaged, connection between inner ear and brain
Two tone suppression
A decrease in the firing rate of one auditory nerve fiber due to one tone, when a second tone is present at the same time especially when second (suppressor) tone has a lower frequency than the first tone
Rate saturation
The point at which a nerve fiber is firing as rapidly as possible and further stimulation is incapable of increasing the firing rate
