Chapter 11-Introduction to the auditory system Flashcards
What is the physical aspect of sound?
Pressure changes in the air- or other physical mediums
What is the perceptual aspect of sound?
The experience of hearing
If a tree falls in the woods and no one is around to hear it; is there a sound according to the physical aspect
Yes there’s a sound bc here was a change in air pressure
If a tree falls in the woods and no one is around to hear it; is there a sound according to the perceptual aspect?
No there was not a sound because nobody was around to experience the tree falling
What is condensation?
AKA compressed
When a force pushes surrounding air molecules together causing a slight increase in air molecule density around the origin of the force leading to an increase of air pressure above atmospheric pressure
Do air molecules move during condensation and refraction?
Not a lot- similar to if a small boat floating in a puddle is interrupted by a pebble falling, the boat will bob up and down
What is rarefaction?
when there is a decrease in density of air molecules following condensation, resulting in lower air pressure
What does a cycle of rarefaction and condensation cause?
a soundwave
What kind of soundwaves are pure tones?
Sine waves
What is a frequency?
The amount of cycles per second that pressure changes repeat
What pitch does a higher frequency usually have?
Usually a higher pitch
What is the frequency of a pure tone/sine wave?
1/t (Hz)
What is amplitude?
The difference of the pressure change between the high and low peaks of a sound wave
What is the result of a larger amplitude
A louder sound
What represents a pitch change
darkening–> increased pressure
Lightening–> decrease in pressure
How is amplitude measured?
decibels–> this is a physical measurement
What range of Db can humans tolerate
0dB (barely audible) 160dB- pain threshold (jet plane taking off)
What is the connection between dB, loudness and amplitude
Amplitude is the change between the highest and lowest points of a wave. The larger the change in amplitude, the louder the sound. Loudness is dependent on the frequency of the wave and the dB This sound is measured in dB.
Can pure tones vary in frequency?
yes
How are frequency and pitch connected?
The frequency of a sound is linked to the perception of pitch. So a high frequency is equal to a high pitch.
What is a key difference between frequency and pitch?
Frequency is physical and can be measured. Whereas pitch is perceptual and cannot be measured- therefore it is very subjective
Define tone height
a perceptual experience of increasing pitch as sound frequency increases.
How we perceive pitch
this is the basis of the music industry
What is an example of tone height?
Keyboards have repeating notes A-G. These notes that are repeated but sound different are an octave apart and have the same tone chroma
Define an octave?
Describes music notes and other sounds
What is the audibility curve?
A threshold for Hearing (dB) vs Frequency (Hz)
What is Timbre
The quality that allows us to find a difference between two tones with the same loudness, pitch and duration
What is an additive synthesis?
multiple frequencies that make up complex tones
depends on the harmonic structure and the attacks and decays of the tones harmonics
What is the effect of the missing harmonic?
The timbre changes when a harmonic is missing. However it does not changed the perceived pitch
What is the attack of tones?
The build-up of sound of a tone
Not necessarily at the beginning of the note- depends on the instrument
ex. when a piano plays the notes are high attack at the beginning because intensity comes at the beginning from the hammer hitting the string. Whereas an organ has a high attack at the end of a note because the intensity builds.
What is the decay of tones?
The decrease in sound at the end of a tone
Define Periodic
a pattern of pressure changes that repeat
ex. musical notes/pure tones
Define aperiodic
a pattern of sound waves that does not repeat
ex. a door slamming
What does the outer ear consist of?
Pinna
auditory canal
Eardrum/tympanic membrane
What does the middle ear consist of?
Ossicles- malleus, incus, stapes
middle ear muscles
oval window
What does the inner ear consist of?
Semicircular canals
Round window
cochlea
What is the pinnae?
the part of the ear on the outside of the head
What is the function of the auditory canal?
to amplify sound within 2000-5000 Hz via resonance
Define resonance
when sound waves are reflected off the tympanic membrane to create constructive interference with oncoming waves.
What is the tympanic membrane/eardrum?
found at the end of the auditory canal and borders the middle and outer ear
What is the general function of the middle ear?
To amplify sound
What are the ossicles?
Three of the smallest bones in the body
consist of the melleas, incus and stapes
What are the functions of the ossicles bones?
They are responsible for amplifying sound
Connect the tympanic membrane to the cochlea
What is the order in which the ossicle bones are found from closest to the outer ear to closest to the inner
Malleas, incus, stapes
What are the common names for the mallaes, incus and stapes in that respective order?
hammer, anvil, stirrup
What is the purpose of muscles in the middle ear?
they dampen the vibrations of the ossicles
How does amplification in the middle ear work?
The vibrations are concentrated by the ossicles to a smaller are this increases the pressure from the vibrations by aprox 17 times
Why is amplification so important in the middle ear?
Because the inner ear is full of fluid, therefore if vibrations are not strong , there is no way that sound can pass through to the inner ear
Why do fish lack outer and middle ear structures?
Because they live in water- water and the fluid found in the cochlea/inner ear have similar densities
What is found in the inner ear?
the cochlea
organ of corti
Hair cells
basilar membrane
apex
How is the cochlea built?
split into two structures by the cochlear partition. These two structures are known as the scala vestibuli and the scala tympani
Where is the organ of corti found?
On the outer spiral of the cochlea
What is the function of the organ of corti?
Where transduction for sounds takes place–> sounds turn into neural activity
What are the two parts the cochlea is broken into?
Scala vestibuli
Scala tympani
How are the scala vestibuli and scala tympani different
The scala vestibuli is the top half of the cochlea and extends from the oval window to the apex. Whereas the scala tympani is the bottom half of the cochlea and extends from the round window to the apex
what is found in the organ of corti?
one row of cilia
three rows of outer hair cells
What is found in the scala media?
Fluid
What is the difference between inner and outer hair cells in the organ of corti?
inner hair cells diverge, with each cell connecting to 8-30 auditory nerve fibres. Whereas outer hair cells converge, so each auditory nerve is connected to multiple outer hair cells
How is the transduction process initiated?
Cilia, connected to hair cells bend which is how transduction starts
How does information get through the cochlea?
- The stapes vibrates, making the oval window vibrate. 2. This causes pressure changes in the cochlear fluid.
