Sound Waves and Ear Function

Audition (Hearing)

• Sound waves are how we hear.
• Amplitude (height) of a wave correlates to loudness.
• Loud sounds have high amplitudes.
• Softer sounds have low amplitudes.
• Pitch is a tone's perceived highness or lowness, dependent on frequency.
• Frequency is the number of wavelengths passing a point in a period of time.
• Low pitch/frequency sounds are bass.
• High pitch/frequency sounds are high-pitched.
• Thunder and lightning are low frequency.
• Mouse squeaks are high frequency.

Outer Ear

• Pinna (external part of the ear) catches sound waves.
• Ear canal channels sound waves to the middle ear.

Middle Ear

• Eardrum (Tympanic membrane) vibrates when sound waves hit it.
• Eardrum can rupture from high pressure or loud sounds.
• Ossicle bones (hammer, anvil, stirrup) pick up vibrations and transmit to the inner ear.

Conduction Hearing Loss

• Caused by damage to the structures that conduct sound waves through the outer and middle ear.
• Damage to eardrum.
• Damage to ossicle bones.
• Damage to auditory canal.

Inner Ear

• Cochlea is a spiral, fluid-filled tube that produces nerve impulses in response to sound vibrations.
• Oval window is the cochlea's membrane-covered opening.
• Basilar membrane is the inner lining of the cochlea where hair cells are located.
• Hair cells (Cilia) are sensory receptors that bend in response to sound vibrations and are triggered in the auditory nerve.
• Hair cells (Cilia) are permanently damaged with prolonged exposure to loud noise.
• Ringing in the ears is a sign of stressed/injured hair cells.

Tinnitus

• Chronic ringing in the ears.
• Caused by damage to and loss of tiny sensory hair cells in the cochlea.
• Tends to happen as people age.
• Can also result from prolonged exposure to excessively loud noise.

Auditory Nerve

• Sends neural impulses from the cochlea to the temporal lobe for processing.

Sensorineural Hearing Loss

• Caused by damage to the cochlea's hair cells or to the auditory nerve.
• Cannot be reversed.

Cochlear Implant

• Attached to the side of the head and wired into the cochlea.
• Translates sounds into electrical signals that travel up the auditory nerve to the brain.

Loudness

• We detect loudness based on the number of hair cells activated.
• The louder the sound, the greater the number of activated hair cells.

Frequency

• The number of complete wavelengths passing a point in a given time.
• Determines pitch (a tone's highness or lowness).
• Long waves = low frequency/pitch.
• Short waves = high frequency/pitch.

Place Theory

• Higher and lower tones excite specific areas of the cochlea's basilar membrane.
• We process pitch based on which part of the cochlea responds to incoming sound waves.
• Front of cochlea responds to higher pitches.
• Deeper areas of cochlea respond to lower pitches.

Frequency Theory

• The brain detects pitch by monitoring the frequency of neural impulses traveling up the auditory nerve.
• Basilar membrane vibrates with incoming sound wave.
• This triggers neural impulses at the same rate as the sound wave's frequency.
• If the sound wave has a frequency of 100 waves per second, then 100 pulses per second travel up the auditory nerve.

Volley Principle

• Various neurons can alternate firing in rapid succession.
• Can achieve a combined frequency above 1000 waves per second.
• Similar to soldiers alternating fire to keep shooting while others reload.

Locating Sounds

• Ear placement allows for stereophonic (multi-directional) hearing.
• A sound to the right hits the right ear more intensely and is received slightly sooner than the left ear.

Vestibular Sense

• Monitors the head's position and movement so the body knows its position in space.
• Fluid in the semicircular canals and vestibular sacs of the cochlea moves when the head rotates or tilts.
• Hair-like receptors send signals to the cerebellum for processing.
• Fluid takes time to settle resulting in dizziness.

Vision

• Eyes detect light waves and transduce them into electrical signals.
• Humans can only see a small portion of the electromagnetic spectrum.

Wavelength

• Distance from one wave peak to the next.
• Determines perceived color.

Amplitude

• Wave's height.
• Determines perceived brightness (intensity).

Eye Anatomy

• Pupil: adjustable opening allowing light to pass through.
• Iris: colored muscle surrounding the pupil, controls pupil size.
• Cornea: clear, protective outer layer where light enters the eye.
• Lens: transparent structure behind the pupil that changes shape to help focus images on the retina.
• Retina: light-sensitive inner surface of the eye; photoreceptors (rods and cones) detect light.
• Fovea: point of central focus in the retina with the highest acuity (sharpness).
• Optic nerve: nerve carrying neural impulses from the eye to the brain.
• Blind spot: where the optic nerve leaves the eye; no receptors.
• Optic chiasm: point in the brain where optic fibers from each eye cross over.
• Thalamus: first stopping point for incoming sensory information except for smell.
• Primary visual cortex: where visual input is first processed in the occipital lobe; main area for processing vision.

Feature Detectors

• Neurons in the visual cortex respond to stimulus features like shape, angle, or movement.

Parallel Processing

• Processing multiple aspects of a stimulus simultaneously.
• Brain integrates aspects into a whole image.
• Examples include color and motion.

Trichromatic Theory

• Retina contains three color receptors: red, green, blue.
• Combinations of these receptors produce perception of any color.

Colorblindness

• Inability to see colors in a normal way.
• Caused by impaired functioning of red-green cones (or rarely blue cones).

Opponent-Process Theory

• Ability to perceive color is controlled by three types of cells with opposing colors: red-green, yellow-blue, white-black.
• These detect only one color at a time.

Gestalt Principles

• Gestalt: organized whole where psychologists emphasize a tendency to integrate pieces of information into meaningful wholes.

Gestalt Principles of Grouping

• Proximity (grouping nearby objects)
• Similarity (grouping similar objects)
• Closure (filling in gaps to see a complete shape)
• Continuity (perceiving smooth, continuous paths rather than abrupt changes)

Figure-Ground Perception

• Organization of visual field into figures that stand out from the surroundings.

Depth Perception

• Binocular Cues:
  • Retinal disparity (comparing images from each eye to compute distances).
  • Convergence (eyes turning inward for closer objects).
• Monocular Cues:
  • Linear perspective (parallel lines appear to converge with distance).
  • Interposition (one object blocking the view of another object).
  • Relative size (smaller objects appear further away).
  • Motion parallax (closer objects appear to move faster than farther objects).

Motion Perception

• Stroboscopic movement (brain perceives slightly varying images as continuous movement).
• Phi phenomenon (illusion of movement when two or more adjacent lights blink on and off in quick succession).

Perceptual Constancy

• Shape constancy (perceive familiar objects as having constant shape even with changing views).
• Size constancy (perceive familiar objects as having constant size even from varying distances).

Sensation and Perception

• Relation between sensory information and our brain's interpretation.

Bottom-Up Processing

• Input processing; brain not assigning meaning initially but taking in sensory info.

Top-Down Processing

• Previous knowledge and experience to assign meaning to sensory stimuli.

Stroop Effect

• Delayed reaction time when asked to name the colour of words, rather than the word itself; Top-down processing recognizing the word first creating a delay.

Selective Attention

• Focusing awareness on a particular task or stimulus.

Distracted Driving

• 28% of traffic accidents involve texting while driving, and this percentage is increasing.
• Passenger or phone distraction accounts for 58% of teenage car crashes.

Cocktail Party Effect

• Ability to focus auditory attention on a particular voice or sound while filtering out others.

Inattentional Blindness

• Inability to see visible objects when attention is focused elsewhere.
• Change blindness (failing to notice changes in the environment).

Transduction

• Sensory input conversion into electrical impulses used by the brain to process information.

Psychophysics

• Study of relationship between physical stimuli and resulting sensations/perceptions.

Signal Detection

• Predicting when and how a faint stimulus can be detected amid background noise. - Detection depends on person's experience, expectations, motivation and alertness.

Difference Threshold (Just Noticeable Difference)

• Minimum amount a stimulus has to change before a person detects the change.
• Increases with the size of the stimulus.

Weber’s Law

• To perceive a difference between two stimuli, the stimuli need to differ by a constant percentage, not a constant amount.

Sensory Adaptation

• Reduced responsiveness when continuously exposed to a stimulus.

Subliminal

• Below conscious awareness; exposure to a stimulus subconsciously affects later responses.

Perceptual Set

• Tendency to perceive one thing, and not another, based on past experience and expectations.

Emotion

• Influences our perceptions. Emotions such as anger or sadness can affect our judgment of objects or situations.

Motivation

• Influences our perceptions of neutral stimuli. Motivations like needing water or needing to get somewhere further can shape our experience.

Context

• The situation where something happens can affect our perception and how meaning is assigned.

Extrasensory Perception (ESP)

• Perception without sensory input; lacks a scientific basis.

• Telepathy (mind-to-mind communication).

• Clairvoyance (perceiving events without witnessing them).