12 - Sound Flashcards
What is a single sound wave caused by? (Sound Cognitive)
An increase in pressure at certain points in an elastic medium, causing a domino effect outwards
How are a series of sound waves generated? (Sound Cognitive)
Perturbation of the domino effect being repeated periodically, a series of sound waves are generated
How do sound wave propagate? (Sound Cognitive)
Sound waves propagate in all 3 dimensions of the atmosphere at equal speeds in all directions, so they are known as spherical waves
At what speed do sound waves propagate? (Sound Cognitive)
It depends on raw type, temperature and pressure of the medium through which it propagates
In dry air at 20℃, what speed do sound waves propagate? (Sound Cognitive)
343 m/s
How can sound waves be represented? (Sound Cognitive)
Temporal variations of sound pressure at a fixed point in space
How are most sounds generated and what does this mean? (Sound Cognitive)
By oscillators, so most sounds are periodic
What is the period of a sound wave? (Sound Cognitive)
The duration of an oscillation cycle, measured between 2 peaks
What is the frequency of sound? (Sound Cognitive)
The number of air pressure oscillation cycles per second
What is the frequency known as? (Sound Cognitive)
The multiplicative inverse of the period
What is the equation for frequency of sound waves? (Sound Cognitive)
F = 1 ÷ T
F = frequency T = Period of sound
What is the amplitude of a sound wave? (Sound Cognitive)
The magnitude of the change of pressure within a wave
What does the amplitude of a sound wave correspond to? (Sound Cognitive)
The maximum amount of pressure at any given point in the sound wave
What is the loudness of a sound wave? (Sound Cognitive)
Perceptual correlate of amplitude
What do spectrograms do? (Sound Cognitive)
- Represent sound waves
- Visualise the distribution of energy across two dimensions
What represent energy distribution? (Sound Cognitive)
Spectrums
What are the simplest form of sound waves and what are they characterised by? (Sound Cognitive)
- Pure tones
- Only have energy at one frequency (one wave)
- Limited at transmitting information only
What do most sounds from humans and animals generate and how are they characterised? (Sound Cognitive)
- Periodic sounds
- Energy at more than one frequency
What does the outer ear do? (Sound Cognitive)
Captures sound signal, amplifies mid-frequency and vertical direction coding
What does the middle ear do? (Sound Cognitive)
Protection, impedance matching
What does the inner ear do? (Sound Cognitive)
Frequency analysis and transduction
In the outer ear, what does the pinna do? (Sound Cognitive)
Affects high frequency sounds by interference between the echo reflected off its different structures
What does the meatus link and what is it also known as? (Sound Cognitive)
- Pinna to the eardrum
- Also known as the ear canal
The middle ear is a cavity made up of what? (Sound Cognitive)
- Ossicles (small bones)
- Malleus (hammer)
- Incus (anvil)
- Stapes (stirrup)
What is the function of the middle ear? (Sound Cognitive)
Transmits vibrations from the ear drum to a smaller oval window
How does the middle ear relate to impedance matching? (Sound Cognitive)
Enables air vibrations (sounds) to be efficiently transmitted into fluid vibrations
What would happen if there was no middle ear? (Sound Cognitive)
Most sound would bounce off the cochlea
What is the main part of the inner ear? (Sound Cognitive)
The cochlea
What is the purpose of the cochlea in the inner ear? (Sound Cognitive)
- Transform a mechanical signal to a neural response on the 8th cranial nerve
- Snail shaped, chambered tube
What are the chambers on the cochlea in the inner ear known as? (Sound Cognitive)
Scala
What are scala separated by in the inner ear? (Sound Cognitive)
Basilar membrane, on top of the organ of corti
What does the arch in the middle of the organ of corti do? (Sound Cognitive)
Separates the inner hair cells from the outer hair cells
What are hair cells known as in the organ of corti? (Sound Cognitive)
Stereocillia
What is the difference between the stereocillia on the outer hair cells and the inner hair cells? (Sound Cognitive)
- Outer = embedded in the membrane
- Inner = free and moved by fluid (endolymph)
How is the cells voltage increased? (Sound Cognitive)
- Hairs bend toward the tallest sterocilium
- Voltage increased
- Increase in release of neurotransmitter
- Auditory nerves connected to the hair cells increase firing rate
