Auditory Systems Flashcards
What two types of vibrations are there?
Periodic (simple and complex tones) and aperiodic (noises)
What are periodic vibrations?
Compressed air molecules which continuously bump next one with sith sound, eg. stereo speakers. Vibrations travel from bumping neighbouts, not the molecules themselves. Repeating waves in periodic vibrations called simple tone have a sinusoidal curve
What type of curve does simple tone periodic vibrations have?
Sinusoidal curve
What is another word for hearing?
Audition
What are decibals?
A logarithmic scale of the amplitude of sounds
What makes complex tones different from simple tones?
COmplex tones are repeating periodic vibrations, but they are without the repeating sinusoidal curve. They have a fundamental frequency (which sets pitch for sound) and amplitude of harmonics sets the quality of sound.
What are the harmonics of sound?
Quality
What is the fundamental frequency in sound?
It sets the pitch for the sound.
What is aperiodic vibrations?
Noise, there are continuous distributions of energy across wavelengths.
What is white noise?
A type of aperiodic vibration that contains all frequencies
What is pink noise?
A aperiodic vibration that contains mid frequencies
What is brown noise?
An aperiodic vibration that contains low frequencies.
What type of sound quality do noises (aperiodic vibrations) not have?
Pitch
What property of the wave encodes pitch?
Frequency
What are the three parts of the ear?
OUter ear Middle ear (bones and muscles) Inner ear (where transduction takes place)
What do the pinna and auditory canal work to do? What are they not good at and what is the consequence of this?
Channel sound. They are not so good gathering sounds from behind pinna, which gives sound directionality.
What is conductive hearing loss?
Problem with middle ear (usually ossicles)
What are the three ossicles in order from outside to inside?
Malleus
Incus
Stapes
What does the stapes push against?
The oval window on the cochlea
What is the malleus ossicle connected to?
The tympanic membrane (eardrum)
What is the diameter of the motion back and forth of the tympanic eardrum?
The diameter of a hydrogen atom
Why doesn’t sound travel well through different mediums? What are the implications of this in the ear (and how does it overcome this?)
Impedence causes only 3% of sound amplitude to get through tympanic membrane. The middle ear overcomes impedence mismatch problem by multiplying vibrations by 24.2x, almost back to 100%
How does the middle ear overcome the impedence mismatch problem?
Surface area ration between malleus and eardrum, and stapes and oval window (18.6x greater SA). Also the lever principle where different lengths of bones which amplifies vibrations by 1.3x
In a nutshell: surface area and the lever principle
What does the eustachian tube do?
Stabilizes pressure between outer and middle ear. The tympanic membrane works best at equal pressure. Eustachian tube collapses during flight and causes tympanic membrane to bulge in
What is the tensor tympani?
The muscle attached to malleus
What is the stapedius muscle?
Contracts in response to loud noise and stiffens up ossicles so that big, low vibrations don’t make it into cochlea very well. Protects hair cells. Attached between stapes and incus. Responsible for the stapedius acoustic reflex. Takes about 50-100 msec for this reflex.
What are the round and oval window?
The oval window is what the stapes presses on and the round window is uncovered and releases extra pressure in the lower chamber. The round window pushes out when the oval window is pushed in.
What is perilymph and where is it found?
Perilymph is fluid in the scala vestibuli (upper) and scala tympani (lower) chambers. It is very sodium rich but doesn’t have much potassium, similar to CSF and may be filtrate
What connects the scala vestibuli and the scala tympani?
Helicatrema channel
What does Reissner’s membrane separate?
The scala vestibuli from the scala media