Chapter 11 Flashcards
What is the physical definition of sound?
Sound is pressure changes in the air or other medium
What is the perceptual definition of sound?
Sound is the experience we have when we hear
What is compression?
When air molecules get pushed together
Causes a slight increase in the density of molecules
Local increase in pressure
What is rarefaction?
Air molecules spread out
Causes a slight decrease in air pressure
What is a sound wave?
The pattern or air pressure changes, which travels through air at 340 m/s
What is a pure tone?
Occurs when changes in air pressure occur in a pattern described by sine.
What is frequency?
The number of cycles that the pressure changes and repeat per second
What is amplitude?
The size of the pressure change
What is a periodic waveform?
A wave that repeats itself
What is fundamental frequency?
The repetition rate
What is the first harmonic?
Equal to the fundamental frequency
What are higher harmonics?
Pure tones with frequencies that are whole-number multiples of the fundamental frequency
What are frequency spectra?
A plot indicating the frequency of the waveform
Provide a way of indicating a complex tone’s fundamental frequency
What is loudness?
The perceptual quality that is most closely related to the level or amplitude of an auditory stimulus
What is the audibility curve?
Indicates the threshold for hearing versus frequency and indicates that we can hear sounds between 20 and 20 000 Hz but we are most sensitive to frequencies between 2000 and 4000 Hz
What did Stevens find about audition?
He used magnitude estimation to show the relationship between decibels and loudness.
Loudness was judged relative to a 40 dB SPL tone
A pure tone that sounds 10x louder than the 40 dB SPL tone would be judged to have a loudness of 1-
Increasing dB by 10 doubles the loudness
What is the auditory response area?
We can hear any tones that fall within this area
At intensities below, we cannot hear the tone
At the upper boundary, there is the threshold of feeling = tones with these high amplitudes we can feel because they are painful
What are equal loudness curves?
Indicate the sound levels that create the same perception of loudness at different frequencies
What is pitch?
The perceptual quality we describe as high or low
A property of auditory sensation in terms of which sounds may be ordered on a musical scale extending from low to high
What physical property is pitch related to?
Fundamental frequency
What pitch are low frequencies associated with?
Low pitches
What pitch are high frequencies associated with?
High pitches
What is tone height?
The perceptual experience of increasing pitch that accompanies increases in a tone’s fundamental frequency
What is a tone chroma?
Notes of the same letter sound similar
Every time we pass the same letter on a keyboard, we have gone up an octave
Tones separated by octaves have the same tone chroma
What are notes with the same chroma separated by?
They have fundamental frequencies that are separated by a multiple of two
What is the effect of the missing fundamental?
The pitch remains the same even when the fundamental or other harmonics are removed
What is timbre?
The quality that distinguishes between two tones that have the same loudness, pitch, and duration
What does removing harmonics affect?
The tone’s timbre
What does timbre depend on?
The time course of the tone’s attack and of the tone’s decay?
What is the tone attack?
The buildup of sound at the beginning of the tone
What is tone decay?
The decrease in sound at the end of the tone
What are aperiodic sounds?
Sounds that have waveforms that do not repeat
What are the pinnae?
The structures that stick out from the sides of the head
Helps us determine the location of sound
What is the auditory canal?
A tube about 3 cm long
Protects the structures of the middle ear
Resonance
What is the tympanic membrane?
Keeps the membrane and middle ear a constant temp
What is resonance?
Occurs in the auditory canal when sound waves that are reflected back from the closed end of the auditory canal interact with sound waves that are entering the canal
What is the resonant frequency?
The frequency that is reinforced the most
What does the middle ear contain?
Ossicles
What do the stapes push on to transmit vibrations?
The oval window
Why are the ossicles necessary?
The inner ear contains liquid that is denser than air
Ossicles concentrate the vibrations by about a factor of 20 and act a lever so that the sound pressure increases sufficiently
What do the middle ear muscles do?
The contract in response to loud sounds to dampen the ossicles vibrations to reduce the transmission of low-frequency components and helps to prevent intense low-frequency components from interfering with our perception of high frequencies
What is the main structure of the inner ear?
The cochlea
What is the organ of Corti?
Contains the hair cells
What does the basilar and tectorial membranes do?
Activate hair cells
How many inner hair cells are there?
1 row
3500 hair cells
How many outer hair cells are there?
3 rows
12000 hair cells
What are stereocilia?
At the tips of hair cells which bend in response to pressure changes
Which hair cells are embedded in the tectorial membrane?
Outer hair cells
What happens to the stereocilia when the pressure increases?
They bend to the right so the hair cell is activated and the attached auditory nerve fibers tend to fire
What happens to the stereocilia when the pressure decreases?
They bend to the left and no firing occurs
What is phase locking?
The property of firing at the same place in the sound stimulus
What frequencies cause more vibration at the base of the cochlea?
high frequencies
What frequencies cause more vibration at the apex of the cochlea?
Low frequencies
What is a tonotopic map?
Map of frequencies with high frequencies activating the base of the cochlea and low frequencies activating the apex
What are neural frequency tuning curves?
Determined by presenting pure tones of different frequencies and measuring the sound level necessary to cause the neuron to increase its firing above baseline in the absence of sounds
How is the cochlea’s filtering action reflected?
The neurons respond best to one frequency
Each frequency is associated with nerve fibers located at a specific place along the basilar membrane
What is the cochlear amplifier mechanism?
An active process that takes place in the outer hair cells
What is place theory?
The brain identifies which neurons are responding the most and uses this information to determine the pitch
Based on the relation between a sound’s frequency and the place along the basilar membrane that is activated
What are some arguments against place theory?
Effect of the missing fundamental (removing the fundamental frequency of a complex tone does not change its pitch)
What is the modified version of place theory?
Explains this result by considering how the basilar membrane vibrates to complex tones
What are resolved harmonics?
Lower harmonics that can be distinguished by a peak and frequency information is available for perceiving pitch
What are unresolved harmonics?
Created by higher harmonics resulting in smooth functions that do not indicate the individual harmonics
Result in poor pitch perception
What is amplitude-modulated noise?
Creates a perception of pitch by containing many random frequencies that don’t create a vibration pattern on the basilar membrane that corresponds with a specific frequency
What is amplitude modulation?
The level or intensity of noise is changed so that the loudness of the noise fluctuates rapidly up and down
What is temporal coding?
The major mechanism of pitch perception
What is the pathway of audio to the brain?
Auditory nerves from the cochlea synapse in a sequence of subcortical structures
Sequence begins with the cochlear nucleus, continues to the superior olivary nucleus, the inferior colliculus, and the medial geniculate nucleus
From the medial geniculate nucleus, the fibers continue to the primary auditory cortex in the temporal lobe
What are pitch neurons?
Cortical neurons which respond to a specific pitch
What area is most responsive to pitch?
The anterior auditory cortex
What is presbycusis?
Hair cell damage resulting from the cumulative effects over time of noise exposure, the ingestion of drugs that damage hair cells, and age-related degeneration
Loss of sensitivity is greatest to high frequencies
What is noise-induced hearing loss?
Occurs when loud noises cause degeneration of the hair cells
What is leisure noise?
Activities like listening to music, recreational gun use, riding motorcycles and working with power tools
What is hidden hearing loss?
People with normal hearing who have trouble hearing in a noisy environment
