Unit 3 Flashcards
Sound Can be defined As…
A phys stim OR a perc response
Sound as phys stim
Changes in air pressure/other medium
-Tree falling causes pressure change w/o or w/ someone’s presence to hear it, so it does make a sound
-Ex “lvl sound of 10dB”
Sound as Perc Reponse
Sound is exp while hearing
-Without anyone around to exp the sound of the tree falling, it doesn’t make one
-Ex, “a trumpet pierced the air!”
Sound as Pressure Change / Phys Stim
Movement/vibrations of objects causing pressure changes around said object
Condensation
THe process of pushing air molecules together, causing change in density of molecule
Sound wave
DEC density of air molecules/pressyre via rarefaction in alt H&L patter, impacting neighboring molecules
-~340meters/s, 1500m/s in water
Pure Tones
Simple sound waves, when pressure changes in air occur in pattern of sine wave
-Can be found in ENV
Amplitude
Size of pressure changes & frequency in sound
Frequency
The number of times/sec pressure changes repeat
Decibel - dB
Unit of sound, 1 dB = 20 X logarithm(p/po) (p = sound pressure of stim, Po = standard sound pressure)
Sound Pressure Lvl (SPL)
20 microspascals
-Multiplying pressure by 10 adds 20dB
-See notes for table
Frequency
of cycles per second causing repeating changes in pressure, the phys measure for perc of pitch
-Measured in Hz (1 cycle/s)
-Ex, a X5 repeat in one sec = 5-Hz
-Humans = 20Hz-20,000Hz
Periodic Tone
Waveform repeats as a property, creating a complex tone
-Consist of pure tones
-Built via additive synthesis
Fundamental Frequency
The rep rate of a complex tone
Additive Synthesis
of sine-waves components added together, creating a complex tone
-Beginning via pure tones
Harmonics
Additive tones, adding fundamentals (first harmonic) and higher harmonics = waveform of complex wave
Frequency Spectra
Indicates a complex tone’s fundamental frequency and harmonics w/out drawing waveform
Removing a harmonic…
Changes a tone’s waveform but repetition remains the same b/c fundamental frequency. Removal = space where waveform holds info indicating fundamental frequency.
Loudness
Quality movement related to amplitude / sound pressure / lvl of audio stim
Pitch
The perceptual quality describing H/L, attribute of audio sensation
-Similar to phys property of frequency
-L fundamental frequencies ass w/ L pitch, H w/ H
-Determined by harmonic spacing and repetition of waveform indicating fundamental frequency
Tone Height
Perc exp of INC pitch accompanies INC in tone fundamental frequency
-L at left end of piano (27.5Hz), INC up to the right end (2166Hz) (perc of INC in tone height)
-ABDCDEFG repeats going up tone height
Tone Chroma
Notes w/ same letter, going up/down an octave interval
-A1 fundamental frequency of 27.5Hz, A3 is 110Hz
Effect of the Missing Fundamental
Constancy of pitch, even w/ removal of fundamental or harmonics, leaving per of periodicity of pitch
Periodicity Pitch
Pitch percieves when fundamentals/other harmonics are removed
-# of consequences, ex speaking on the phone (phone can’t produce actual male pitch of below 300Hz, makes a similar sound)
Range of Hearing
One’s specific range of frequencies able to hear
Audibility Curve
Human range of hearing, indicates threshold for hearing (via free-field presentation)
-Btwn 20Hz-20,000Hz
Auditory Response Area
Area of tones we can hear
-Animals can hear other ranges from below 20Hz (elephants) to as high as 150,000Hz (dolphine)
Audibility curve & response area indicate pure tone loudness w/:
Sound pressure & frequency.
Equal Loudness CUrve
Rltnsp btwn loudness and frequency. Determined by presenting standard tone of one frequency and dB then listener adjusts lvl of tone w/ frequency to match loudness
-Tones at 30dB-50,0000dB = in loudness between, those of 80dB are equally loud between those frequencies
Timbre
Perc quality of tone, distinguishing btwn 2 tones w/ same loudness, pitch, and duration while sounding diff. Depends on time course of tone’s attk and decay.
-Flute vs bassoon playing same note w/ same loudness, flute = clear and mellow, bassoon = nasal or reedy = timbre, despite same loudness, pitch, and duration
-Relates to harmonic structure of a tone
-Diff in strengths/number of harmonics
-Depends on harmonic structure & time course of attack and decay of tone’s harmonic
Attack and Decay
Attk - Build up of sound at beginning of tone
Decay - DEC in sound at end of tone
First and last 1/2 second of tone are imptnt to distinguish tones, playing backwards impacts too
Aperiodic Sounds
Sounds w/out repeating sound waves
Basic tasks of the ear
-Deliver sound stim to receptors
-Transduce stim from pressure changes into electrical signals
-Process electrical signals so they can indicate qualities of the sound sources (ex, pitch, loudnesss, timbre, and location)
Ear systems
Outer, Middle, and Inner
Outer Ear
Works to protect ear and intensify sound via resonance. Contains:
Pinnae, auditory canal, eardrum/tympanic membrane
Pinnae
Structure sticking out the side of the head. Determines sound location, isn’t necessary for hearing tho
Auditory Canal
TUbe-like structure (recess) 3cm long, protecting delicate ear from outside hazards) w/ wax
Resonance
When sound waves reflect back from the closed end of auditory canal, interacting w/ sound waves entering the canal, rein sound frequency
-Resonance Frequency - Frequency most, depending on length of canal
-Amplifies effect on frequencies btwn 1000-5000Hz
Middle Ear
Small cavity, 2 cubic cm in volume, separates inner and outer ear containing ossicles and muscles
Ossicles
3 smallest bones in body
Malleus - AKA hammer, sets vibration via eardrum to the incus
Incus - AKA anvil, transmits vibrations into stapes
Stapes - AKA stirrup, transmit to inner ear via pushing on membrane covering oval window
Ossicle, liquids, & necessity
Ossicles are necessary b/c middle and outer ear are filled w/ air while inner contains liquid.
The liquid in inner that is H in density + L density air from outer and middle ear = vibrations. W/out middle ear, LT 1% would be transmitted.
Effect of ossicles concentrating vibrations of tympanic membrane/eardrum onto stapes & being hinged to crt lever action is similar to when a fulcrum is placed under a board, pushed on the long end to lift it
Middle Ear Muscles
Smallest skeletal muscles in body, attatched to ossicles, contracting at H sound intensities, protects ear from poss dmging stim
Inner Ear
Liquid filled cochlea, shaped like a snail, unrolled = 2mm in diameter, 35mm long. Liquid inside vibrates via stapes mvmt against oval window
Unrolled cochlea divides into:
Scala vestibuli - Upper half of uncoiled cochlea
Scala tympani - Lower half of uncoiled cochlea, extending from base near stapes to apex
Organ of Corti
Large structure in cochlea containing hair cells, receptors for hearing
Cilia
Protruding tops of cells, where sound acts to produce electrical signals
-Inner hair cells: ~3500
-Outer hair cells: ~12,000
-Bending of cilia inner hair cells responsible for transduction
Basilar Membrane
Supports organ of corti, vibrates in response to sound
Tectorial Membrane
Extends over hair cells
The In-out bending of cilia b/c stapes cause pressure change, causing:
-Organ of corti into up-down vibration
-Tectorial membrane moving back and forth
-The bend of inner hair cells
Bending Cilia…
One movement opens channels, allowing ion flow, while the other direction causes shut (no signals). Amount cilia bend necessary for response is extremely small (as small as 100 trillionths of a meter / 100 picometers)
-If ciliar = eiffel tower, bend would be at the pinnacle (IRL 1cm)
-Auditory system can detect movements as small as 10^-11cm. Air pressure threshold is only 10-15dB above air pressure created by random movement of air molecules.
Bekesy’s Place THeory of Hearing
The frequency of sound, indicated by place among cochlea where nerve fires Highest
-L frequencies = MAX activity in hair cell & audio nerve fiber at apex end
-H frequencies = Max at hair cells and audio nerve at base of membrane
-Concluded by determining how basilar membrane vibrates in response to diff frequencies
Traveling Wave
Motion of basilar membrane similar to when one holds the end of a rope and “snaps” it
Basilar membrane apex VS base size & stiffness
Base (closest to stapes) is 3-4X narrower and 100X stiffer than apex
Envelope of Traveling Wave
Indicates MAX displacement caused via traveling waves at each point along the membrane
-Max displacement imptnt b/c hair mvmnt depends on membrane displacement
-Has peak at one point on basilar membrane
-Position of peak is function of frequency of sound
Place Theory Evidence
Place on cochlea linked w/ frequency of tone, measuring electrical response of cochlea, hair cells, and audio nerve fibers
Tonotopic mapping - Orderly map of frequencies along length of cochlea
Auditory Masking (evidence for place theory)
Exp where sound is masked/DEC/Muffled by others
-Threshold for frequencies near ^ are most raised, curve isn’t symm.
-Spreads to more H than L frequencies
Basilar membrane vibrations into complex tones
Basilar membrane responds to complex tones, vibrating to fundamental and harmonics at places associated w/ frequency of each harmonic.
Updating Bekesy’s THeory
Two close frequencies can overlap and ID patterns of vibration. Psychophys allow us to distinguish sm diff in frequency. Bekesy rsch w/ cadavers, recent tech is more rsch so there is less overlap than he suggested.
Healthy cochleas would have vibrated more sharply.
Cochlear Amplifier
VIbration of membrane, cilia of outer hair cell bend in one direction, elongate, pull on basilar membrane > basilar memrane motion INC and sharpens response to specific frequencies
Timing of neural Firing can Signal Frequency
Hair cell in synchrony w/ rising and falling pressure of sound stim, may not fire at all INCs b/c needs rest after firing
Phase Locking
Firing at same place in sound stim
-Firing in bursts, separated by silent intervals and timing of these matches frequency of stim
Temporal Coding
Connection btwn freuqency of sound stim and timing of audio nerves, ~4000Hz
Hearing Loss Types
Conductive
Sensorineural
Conductive hearing loss
Blocking sound from reaching receptors
Sensorineural hearing loss
Dmg to audio nerve, hair cell, or brain. Includes presbycusis
Presbycusis
Loss of sensitivity, “old hearing” ass w/ age, effecting M most
Noise induced hearing loss
When loud noises cause degen of hair cells
-Dmg to organ of corti in those who work in loud ENV
-OSHA mandates no more than 8hr of exposure to +85dB
Leisure noise
What is heard when INC volume on MP3 player, recreational fun use, playing musical instrument, working w/ power tools, play in rock/pop bands, , and attend sport events (hocket games can be 90dB for ~3h)
From the Cochlea to the Cortex: pathway
Audio nerves from cochlea syn in sequence of subcortical structures.
SON (superior olivary nuclei) in brain step
-IC (inferior colliculus in midbrian)
–MG (medial geniculate, thalamus)
to the audio receiving area (A1) in temporal lobe
Function of Colro
Make things look appealing, emotion detection, emotion elicitation, signaling others, Perc organization
Jock Locke & Color
Color lacks primary qualities (real, phys like weight or shape) but instead has secondary qualities (color)
Electromagnetic Waves
Produced via sun light, make of electrical and magnetic components
Electromagnetic Spectrum
Consists of magnetic waves in short & long frequencies
Color relates to wavelength
Blue & violet = 400-500nm
Green & yellow = 500-600nm
Orange & red = 600-700nm
Color Perc
Interaction btwn matter & sunlight
-Reflection, transmission, and absorption of WLs
-Perc via WL hitting eye is relfected
Color Qualities
Hue
Saturation
Value
Hue
All color have hue, natural order:
Red, Y, G, B, violet
-B&W have no hue
-Can discriminate btwn 200
Saturation (chroma)
Degree of hue separating from white
-Colors light in saturation = weak
-20 saturation vlaues
We can discriminate btwn ~1M colors
Trichromatic THeory
Young & Helmholtz proposed 3 diff receptors for color vision:
-Bhvrl support - Color-matching exp found obsvr adjusted amounts of 3 WL to match
-Those w/ color deficiency = 1 or 2 WL, not 3
-Phys support - Measured absportion spectra of visual pigment, MAX repsonse to S WL (blue), M WL (green), and L WL (red)
Color Perc is based on
Response of 3 diff cone types, combo of responses in all 3 lead to perc of color
Metamers - Colors similar b/c diff phys WL
Additive VS subtractive color mixing
Add = Adding light
Sub = Paint subtracts
Color Deficiencies
Monochromat only needs 1 WL, dichromat needs 2.
Anomalous trich = Needs 3 WL in diff proportions than norm
Unilateral dich - Trichromat vision in one eye, dichromat in the other
Ishihara Plates = Dotted circle w/ number revealing color blindness
Opponent Processing Theory
Color vision caused by opposing responses, generated by B&Y and B&R
-Bhvr support - Afterimages & simultaneous color contrast show opposing pairs
Types of Color Blindess
R/G
B/Y
Bl/W
Light > receptors (trichromat, color matching ) > Opponent cells (afterimages, simultaneous contrast) > brain
PERC, Color, light constancy, and Ratio principle
Color constancy - We adapt to color & our surroundings
Perc of lightness (lightness constancy) - % of light reflected by object, not amount
Ratio Principle - 2 areas reflecting diff amt look same if ratio of intensities are same
Why is the Sky Blue?
Rayleigh scattering - Sunlight spreads while reflecting on objects, shining blue b/c thin stretch in morning. Orange at night b/c long stretch
