Audition 1 and 2 (sound and the ear) Flashcards
when tuning fork vibrates, it creates air _______ and air _______
Compression and rarefaction/decompression
Sound is produced by ______ fluctuations in the air
Pressure
Sine wave and air pressure
- In up phase of the wave, high air pressure
- Low phase of wave = low air pressure
Amplitude shows the degree of _______
Compression
higher amplitude = _____quieter/louder sound
Louder
higher frequency = _____shorter/longer wavelength
Shorter
Sound pressure/intensity (Pascals) measures …
Force exerted by air molecules.
Loudness
Psychological perception of sound intensity.
* Measured in decibels (dB), relative to the smallest perceivable pressure.
Logarithmic scaling of loudness
Intensity increases faster than decibels
+10 dB = 10× increase in intensity.
0dB = intensity ratio of 1, smallest perceivable pressure
Intensity
How much fluctuation in air pressure there is (in pascals)
Change in sound intensity between 10dB and 20dB
10^3 - 10^2 = 1000-100 = 900 pascals
Air pressure is the … associated with perceived loudness
objective physical phenomenon
Loudness is a _______ perception
Subjective
________ are more representative of our loudness perception
Decibels (dB)
Pitch
The psychological aspect of sound related mainly to the fundamental frequency.
frequency (Hz)
Number of cycles (peak to base) per second.
pure tones
Sounds that only have one frequency
Higher frequency = higher ____
Pitch
different combinations of ______ and _______ level will be perceived with different subjective loudness.
Frequency and pressure
Equal-loudness curve
A graph plotting sound pressure level (dB SPL) against the frequency for which a listener perceives constant loudness.
2 units for measuring objective air pressure
pascal, decibels
phon
Unit used in the equal-loudness curve which corresponds to the dB value of the curve at 1k Hz.
Each of the points on the equal loudness curve will be associated with an equal subjective perception of ________.
Loudness
E.g.
Sounds of 70dB at 0.2 kHz, and 60 dB at 1 kHz will sound equally loud (60 phons).
If 2 sounds have the same ____ number , they will be perceived equally as loud (even if they do not have the same decibels)
Phon
Complex sounds can be described by their _______.
Spectrum
Complex sounds have more than one _______
Frequency
spectrum
- represents the different frequencies of a sound
A simple sine wave can be combined with other simple sine waves to produce more complex waves like a ______ wave
Square
What do x and y correspond to in a spectrum ?
X : frequency
Y : energy
The number of vertical bars in a spectrum correspond to…
The number of frequencies
The length of the bar in a spectrum represents energy or _______in the waveform
Amplitude
Harmonic spectrum
Spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency.
- Typically caused by a simple vibrating source (e.g., string of a guitar)
Fundamental frequency
Lowest-frequency component of a complex periodic sound.
Timbre quality is conveyed by the profile of the _______ : why same note is heard differently across instruments (same for voices)
Harmonics
Timbre
Psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar.
When the space between the bars in a spectrum is _____ , all frequencies are all integer of the fundamental frequency
Even
The pitch is the ______ frequency bar in a spectrum
Lowest (fundamental frequency)
Auditory Canal
A tube-like structure that directs sound waves from the outer ear to the tympanic membrane (eardrum)
Tympanic Membrane (Eardrum)
- thin, vibrating membrane that separates the outer ear from the middle ear
- transmits sound vibrations to the ossicles
- will vibrate at the same frequency as the sound.
Ossicles
- Three small bones in the middle ear (malleus, incus, and stapes)
- amplify and transmit sound vibrations from the tympanic membrane to the inner ear.
If a sound is too loud, a muscle will prevent the ossicles from…
moving too fast
Cochlea
A spiral-shaped, fluid-filled structure in the inner ear that converts sound vibrations into neural signals for hearing.
Oval Window
- A membrane-covered opening that connects the middle ear to the cochlea, transmitting
vibrations from the ossicles
Round Window
A flexible membrane in the cochlea that helps relieve pressure from sound waves traveling through the cochlear fluid (like 2 holes for maple syrup can)
Cochlear (Auditory) Nerve
Nerve that carries auditory information from the cochlea to the brain for sound processing
Organ of Corti
- a structure on the basilar membrane of the cochlea that is composed of hair cells and dendrites of auditory nerve fibers.
- Where sound is going to be transduced, will become action potential
Basilar Membrane
A structure within (middle) the cochlea that vibrates in response to sound and allows frequency discrimination by supporting hair cells.
Tectorial Membrane
- A gelatinous membrane on the basilar membrane in the cochlea that interacts with hair cells, aiding in the conversion of mechanical sound vibrations into electrical signals.
- Right on top of the organ of Corti
Hair Cells
- Sensory receptor cells in the cochlea that detect sound vibrations and transduce them into neural signals. then transmits them to the brain via the auditory nerve.
- Connected to the dendrites of the auditory nerve
Tip links
- On top of hair cells, with potassium channels at one end.
- When they are at rest and upright, all of the potassium’s channels are closed. A plug is blocking the potassium channel
- When a sound that makes the liquid in the cochlea move, they will bend, which pulls on the plug : potassium enters the air cells. If it’s strong enough, the air cell depolarizes and produces an action potential that is transmitted to the auditory nerve, and eventually sent to the brain.
The stapes that’s pushing on the Oval window is going to make the liquid inside of the cochlea move at the same _______ as the airwave.
Frequency
Cochlear place code in individual hair cells
based on where the hair cells that are activated are located
Unfolding the cochlea
- Basilar membrane at the center
- At each level of the basilar membrane, you have different hair cells and fibers of the auditory nerve.
- The auditory nerve fibers that are at the tip or apex of the cochlea are more responsive to low frequencies
en
Temporal coding
Auditory nerve (AN) firing is « phase-locked » neurons systematically fire at a given time point of the cycle.
However, above 4000 Hz – 5000 Hz the refractory period of AN fibers doesn’t allow neurons to fire fast enough.
Every time you arrive at the tip of the wave, it triggers…
a strong action potential throughout the cochlea
In the cochlea, the auditory nerve fibers will fire with the same ______ as the sound that is transmitted through the cochlea.
Frequency
However :
- The neuron in the cochlea is only able to follow the frequency of the sound up to 4000-5000 Hertz
- after that the neuron cannot trigger another action potential because the refractory period of the cell doesn’t allow it to fire more rapidly
Volley principle
Even if individual AN fibers can’t keep the pace, the whole population of neurons can still temporally encode the frequency
- if you add all of their action potentials together, there is a group of action potentials corresponding to each phase of the sound wave. These groups are called Volley
