Auditory Sensation & Perception (8) Flashcards
What makes a sound
When the movements or vibrations of an object cause pressure changes in the air, water or any other medium that surrounds the vibrating object
Tuning fork
Its vibrations produce a single pure tone by causing a SINUSOIDAL change in air pressure
Wavelength
Distance between 2 peaks
Amplitude
Distance from baseline to top of peak
Rarefaction
(Low pressure) particles far away from each other (opposite of compression)
Concentric
Changes in air pressure spread away from the tuning fork in all directions
Frequency = **
1/wavelength
What does frequency determine *
The perceived pitch
What is frequency measured in
Hertz
Amplitude determines.. *
The loudness of a tone
Amplitude is measured in. **
Decibels
Number of dB (decibels) equation ***
Number of dB = 20 x LOG (P/P°)
P is the sound pressure of the stimulus
P0 is a standard reference sound pressure
Why is the dB scale useful?
- It compresses the range of numbers we need to handle
- Relates well to our perception of loudness
How can we tell a piano from a guitar *
Overtones
What are overtones ***
The unique components of their complex sound waves whose frequencies are multiples of the fundamental frequencies of each tone
Outer ear consists of..
Pinna, auditory canal
Pinna
Helps with sound location
Auditory canal
Protects the tympanic membrane (ear drum) at the end of the canal
The middle ear consists of.. *
Malleus (hammer), incus (anvil), stapes (stirrup)
Malleus (hammer)
Moves due to the vibration of the tympanic membrane (ear drum)
Incus (anvil)
Transmits vibrations of the malleus
Stapes (stirrup) *
Transits vibrations of the incus to the inner ear via the oval window of the cochlea
Outer and middle ear is filled with..
Air
Inner ear is filled with..*
Fluid - that is much denser than air
(Pressure changes transmit poorly in this)
Function of ossicles
Act to amplify the vibration for better transmission to the fluid
What do middle ear muscles do?
Protect the cochlea from loud (amplified) noises by changing the strength of coupling between the 3 ossicles
Basilar membrane (inner ear)..
Vibrates with high frequency while the lower, wider parts are softer and respond to lower frequencies
Structures in the cochlea
The basilar membrane and the organ of Corti that contain the outer and inner hair cells and the tectorial membrane
? What does the organ of corti consist of
Cilia + outer hair cells
How does transduction by hair cells occur **
Movement of bundle of cilia in different directions causes either increase/ decrease in the firing rate of an auditory neuron
What allows us to perceive a large range of frequencies? **
The tonotopic organisation of the basilar membrane - where the vibration is tells our brain what sound frequency is (place coding?)
High and middle frequencies are at different places on the basilar membrane
High and middle frequencies on the basilar membrane
Place coding
Low frequencies on the basilar membrane
Rate coding - follows the stimulus vibrations and the rate of firing of auditory neurons (this changes with the frequency of vibration)
Temporal coding
(Localisation of sound) AZIMUTH coordinates
Position left to right
(Auditory localisation) ELEVATION coordinates
Position up and down
Distance coordinates
Position from observer
Azimuth differences
Intensity - our head casts a shadow
Time of onset - differences in time of arrival can be coded - when distance to the ear is the same, there is no difference
Phase - ear drums will be pushed/ pulled at different rates - high frequency will be pushed in, low frequency will be pushed out (distance between ear drums)
Moncaural cue for sound location **
The specific shape of our Pinna and head affect the intensities of different frequencies in a different way
Measured - small microphones in ears and comparing the intensities of frequencies with those at the sound source (spectral cue)
Vestibular system
The sense of balance - a closely related sensory organ that uses hair cells
