• Sound waves are pressure waves in some medium (e.g., air or water)
• Sound sources “push” and “pull” on air molecules, creating mechanical vibrations.

• Sound source will “push” and “pull” on the air molecules 
• Pressure wave is measured by watching ONE spring over time
• push high pressure
• pull lower pressure
  

• The Ear is the entire organ.  It is composed of three parts:
• Outer ear, middle ear, inner ear
• Outer: pinna, auditory canal, typanic membrane
• Middle: ossicles, oval window
• Inner: cochlea, organ of corti, basilar membrane, hair cells, auditory nerve
  

• Part of the Ear that is exposed to the air.

• Outer ear
• amplifies sound
• aids in localizing sounds by amplifying sounds from the front and blocking sounds from the rear

• Outer ear
• protects middle and inner ears
• amplifies frequencies assciated with human speech

• Outer ear
• vibrates in response to sound waves
• transmits vibrations to the middle ear

• Ossicles:(Three small bones)1.Malleus or Hammer 2.Incus or Anvil 3.Stapes or Stirrups

• Middle ear
• Transmit sounds
• Amplify sounds: Oval window is 20X smaller than tympanic membrane. Conservation of energy results in amplified vibrations
• Acoustic Reflex protects Inner Ear: Muscles attached to ossicles clench in loud environments, thereby limiting vibrations

• Sound vibrations stimulate neurons (Hair Cells) in the Cochlea
• Incus & malleus, stapes, oval window, auditory nerve, cochlea
  

• 3,500 Inner & 12,000 Outer Hair Cells
• Cilia on top of cells are attached to Tectorial Membrane.
• Movement of Basilar Membrane and Shearing of Tectorial Membrane activate (by bending) the Hair Cells

• Lower amplitude softer volume
• high amplitude louder volume
• Measure in decibels
• Measuring: dB=20log(p1/p0)
• P1- pressure of sound wave being measured
• P0- pressure of absolute threshold at 1000 Hz

• Low frequency low pitch
• High frequency high pitch
• Measured in hertz
• frequency=#cycles/second=Hz

• In general, sounds with greater Amplitudes will sound louder than those will lower Amplitudes.
• However, the loudness of a given Amplitude will be perceived differently for different frequencies

• Minimum amplitude necessary to hear a sound
• Varies with frequency
• all points on a curve sound equally loud
• below threshold louder
• above threshold softer

• Hair Cells on the Basilar Membrane allow us to distinguish the frequencies of different sounds.

• Uneven
• base is 100x stiffer than apex
• apex is 5x wider than base

• Initially suggested by Hermann von Helmholtz in 1863.
• Structure of Basilar Membrane causes it to vibrate in different locations to different frequencies.
• This will cause different Hair Cells to be stimulated by different frequencies.
• Bekesy (1961) won nobel prize for testing and confirming

• Perceiving where a sound is coming from

• Changes in Amplitude and Frequency allow us to perceive the distance of a sound source

• Friction causes air molecule vibrations to lose amplitude with distance.

• Louder sounds are perceived to be closer

• Sound waves ‘bunch up’ in front of moving source

• Sounds with increasing frequency appear to be approaching.

• Sound waves ‘stretch out’ behind a moving source
• Sounds with decreasing frequency appear to be receding

• Amplitude increases as a source approaches

• 2x amplitude/amplitude velocity= time-to-contact
  

• Binaural Cues allow us to perceive the left-right location of a sound source

• Head casts a ‘sound shadow’

• Amplitude at the ear closest to the source can be 20 dB greater

• Similar principle to binocular depth perception.
• Sounds reach more distant ear later.
• You are sensitive to time differences as small as 0.0001s.

• The auditory system analyzes and then suppresses later arriving sounds for consciousness.
• This amplifies your sense of location.
• This also eliminates errors due to echoes

• Folds in the Pinna alter sounds from different directions

• With Pinna altered by a mold, vertical localization was lost, but was regained after 2-3 weeks

• Chemical senses: receptors for chemicals dissolved in liquid, primarily in the mouth, perception of flavor
• Stimuli: chemical dissolved in water (or saliva), measured in MOLES
• 1 mole= 1 gram of chemical in 1 liter of water

• Chemical senses: receptors for chemicals dissolved in air, perception of smell
• Stimuli: volatile chemicals (dissolved in air)

• Taste buds live on the pappilae
• foliate: folds on back and side
• circumvallette: back of tongue
• filiform: no taste, break down food
• fungiform: tip and sides

• Live on the pappilae
• receptor cells, taste pore, nerve fibers

• Salty-side
• sweet-tip
• sour-tip, sides
• bitter- back
• Umame (meaty)

• Location of smell receptors
• receptors embedded in mucus

• We can perceive 10,000+ odors using 350+ types of receptors
• Henning proposed 6 basic dimensions of smell:
• Putrid (garbage), fragrant (flowers), ethereal (citrus), spicy, burned, resinous (plastic)

• Fish: taste receptors on skin, no distinction between taste and smell
• Amphilbia: Separate taste and smell
• Smell: taste at a distance
• Taste: on skin (fly), in mouth

• Taste: Frontal operculum and insula to orbitofrontal cortex
• Smell: olfactory bulb to olfactory cortex to orbitofrontal cortex

• perceiving the world using receptors in the: skin, muscles, and joints
• divided into: cutaneous (skin alone), kinesthetic (skin and muscles/joints)

• Perception using the skin alone
• perceived by cutaneous touch: pressure, temperature, and pain

• Largest sensory organ: 6' male has about 3000 in^2 (20ft^2)
• most versatile sensory organ: nerve endings, shields body, blocks harmful light, stabilizes temperature

• Differs between males and females
• Face is the most sensitive

• We perceive temperature using cold and "warm" receptors
• Hot is a mixture of cold and warm receptors (temperature illusion)

• nociceptors= pain receptors
• can occur without stimulation
• influenced by emotions, stress, expectations
• people rate pain differently: rate pain of ice water from 1-150
• female athletes: 76
• female non-athletes: 130
• pain may refrer to emotional discomfort rather than physical pain

• in the real world often involves some musical activity: texture and hardness, weight

• Perceiving the locations and movements of body parts
• largey a function of receptors in the muscles
• active touch is more accurate

• rubbing-texture
• pressing-hardness
• resting hand-temperature
• enclosing-size
• contour following-shape
• lifting-weight

• epidermis- dead skin
• dermis- new skin
• hypodermis- fat

• meissner corpiscle: dermis
• merkel receptor: epidermis
• free nerve endings
• ruffini cylinder: dermis
• pacinian corpuscle: deep in skin, intestines, and joints

• Area on skin within which a receptor is sensitive
• small and large
• larger receptive fields lead to greater 2-point thresholds

• merkel receptor: small, pressure
• meissner corpuscle: small, tapping
• ruffini cylinder: larger, stretching
• pacinian corpiscle: large, rapid vibration

• Sensory neurons enter the spinal cord through the Dorsal Root
• travel to the thalamus,
• and then get sent to the somatosensory cortex

• more of the cortex is devoted to more sensitve areas

• Cortical area devoted to a part of the body can change with the experience
• if remove finger, area becomes less sensitive
• stimulate finger, area becomes more sensitive

• Nociceptors: connect to the brain along small-diameter fibers (s-fibers)
• pressure receptors: connect to brain along large-diameter fibers (l-fibers)
• transmission cells: pain signals are carried up spinal cord on transmission cells (t-cells)

• sense organs and nervous system develop after birth

• abilities such a depth perception develop with experience

• 0-2 years: physiological development, feature and form perception
• 2-20 years: eye movements and attention, complex patter recognition (e.g., faces)
• 20+ years: decreased functioning

• At birth: 1/2 volume of adult eye, rods & cones (but fewer and immature), ill-deined fovea, more developed periphery
• one year: receptors have adult-like functioning
• two years: receptors developed and myelinated

• Retinal ganglion cells, LGN, Superior colliculus, & Visual cortex
• At birth: slow responses, silent areas, larger receptive fields, less inhibition, less orientation selectivity and binocularity in visual cortex

• deterime which of two stimuli the infant prefers to look at
• one month: no preference, except for mom
• two months: preference for intact faces

• Habituation: infant will grow bored of viewing the same stimulus
• discrimination test: after hibituation, remove stimulus (say, blue) and replace with new stimulus (say, red), infants who notice a difference will resume looking

• Newborns are able to discriminate: presence, number, size, contrast, curvature
• at 4 months: position, orientation, shape

• Birth: some ability to discriminate long and medium wavelengths, no ability to disriminate short wavelengths
• 2 months: ability to discriminate short wavelengths develops

• tracking: at birth, eyes will tack slowly moving stimuls
• test: present a slowly moving stimulus, if the infant tracks the stimulus, then they can see the image

• distance: newborns can see about 20cm
• acuity: newborns have an acuity of about 20/800
• 20-40 years: 94% have 20/20 vision
• 80 years: 6% have 20/20 vision
  

• experiments on animals with altered perceptual experience show the importance of active experience on development
• restricted rearing: raising an animal without any visual experience
• selective rearing: raising an animal with partial visual experience

• kittens raised in complete darkness
• 4 months: initially appear blind, will regain some visual ability after 2-3 days, will eventually develop noral abilities
• 6 months: will develop some abilities but will never be normal, permanent deficits in; acuity, tracking, avoidance, jumping, & eye blinks to looming stimuli

• with restricted visual experience
• all visual pathways: appear immature, less developed
• decreased cortical funtion: orientation selectivity, movement selectivity, binocularity, acuity

• kittens raised in an environment (e.g., wearing goggles) where they only experience one type of contour (e.g., vertical)
• perceptual: decreased acuity for contours not experienced during development
• physiological: decreased responding for contours not experience during development

• we need more than just experience, we need active experiences
• method: one kitten pulls another in a trolley, same visual experience, but only one is active
• results: normal vision in active cat, no depth perception in passive cat

• 3 weeks to 3 months
• deprivations beginning after this period produce limited effects
• deprivations for as few as 3 days during this period produce significant effects

• smaller pupil
• yellowing lens and cornea
• decreased sensitivity to short wavelengths
• fewer rods and cones

• decreased focusing rance
• 40+ years decreased
• correction=bifocals

Decibels (Db)

·         The units that are used for measuring amplitude

A sound wave consists of changes in this property over time

·         All of the zones that sit along one equal loudness contour will appear to be identical on this perceived dimension

By stimulating pressure receptors

·         Researchers investigated how we perceive the vertical location of sound by manipulating this part of the ear

·         Our brain suppresses later arriving sounds (i.e., echos) and only passes the first sound to reach our ear onto consciousness

The Doppler effect creates increases in this feature of a sound as the sound approaches

Monaural characteristic of a tone that provides information about how far away the sound source is