audio system Flashcards
amplitude
intensity-measured in decibels
loudness
is the perception on intensity
frequency
the number of compressions per second-measured in hertz (Hz)
pitch
is the perception of frequency
hearing range is 15-20,000 Hz for humans
Pinna
the structure of flesh and cartilage attached to each side of the head
outer ear
Tympanic membrane
mid-ear
(eardrum)
-vibrates at the same frequency as the sound waves that strike it.
-Sound waves reach the tympanic membrane through the auditory canal.
-attached to three tiny bones (hammer, anvil, and stirrup)
Hammer (malleus)
a small bone in the middle ear that transmits vibrations of the eardrum to the incus
Anvil (incus)
a small anvil-shaped bone in the middle ear, transmitting vibrations between the malleus and stapes.
stirrup (stapes)
a bone in the middle ear of humans and other mammals which is involved in the conduction of sound vibrations to the inner ear. The stirrup-shaped small bone is on and transmits these to the oval window, medially. The stapes is the smallest and lightest named bone in the human body, and is so-called because of its resemblance to a stirrup
oval window
inner ear
receives vibrations from the tiny bones of the middle ear, and the cochlea
cochlea
inner ear
- snail-shaped structure
- contains three fluid-filled tunnels: the scala vestibule, scala media, and scala tympani
hair cells
- auditory receptors that lie between the basilar membrane and the tectorial membrane in the cochlear
- vibrations in the fluid of the cochlea displace these
- responds within microseconds to displacements as small as 10^-10 meter, thereby opening ion channels in its membrane
- these cells then stimulate the auditory nerve cells (eighth cranial nerve)
basilar membrane
The basilar membrane within the cochlea of the inner ear is a stiff structural element that separates two liquid-filled tubes that run along the coil of the cochlea, the scala media and the scala tympani
tectorial membrane (eardrum)
middle ear
it vibrates at the same frequency as the sound wave that strike it
Auditory Pathway
cochlea—cochlear nucleus— superior olive—medial geniculate nucleus (thalamus)—auditory cortex (temporal lobe)
localization of sounds
- different intensity between each ear ( work best for frequencies above 2-3,000 Hz)
- the difference in the time of arrival at each ear
- phase difference between the ears (see fig 7.9) this works best for low frequencies
frequency theory
-we perceive certain pitches when the basilar membrane vibrates in synchrony with a sound, causing the axons of the auditory nerve to produce action potentials at the same frequency
only works for low frequency
up to 100 Hz
place theory
-each area along the basilar membrane is tuned to a specific frequency and vibrates whenever the frequency is present. Each frequency activates hair cells at only one place along the basilar membrane, and the brain distinguishes frequencies by which neurons are activated.
-DOWNFALL of this theory: the various parts of the basilar membrane are bound together too tightly for any part to resonate like a piano string
4,000 Hz to 20,000 Hz
volley principle of pitch discrimination (mechanism)
the auditory cortex as a whole can have volleys of impulses to about 4000 per second
conductive deafness (middle-ear)
occurs if the bone of the middle ear do not transmit sound waves properly. Causes include diseases, infections,m tumors…
Nerve deafness (inner-ear deafness)
results from damage to the cochlea, hair cells or the auditory nerve. cause include German measles and other diseases during pregnancy, lack of oxygen at birth, inadequate activity of thyroid gland, multiple sclerosis, meningitis, reaction to aspirin (children), and repeated expose to loud noises.
tinnitus
a frequent of constant ringing in the ears. More common in the elderly.
