Title: Sensation and Perception
1Sensation and Perception
- In this part of the course we will try to answer
such questions as - How do we see and hear?
- Why does a TV only need three phosphors (Red,
Green and Blue) to allow us to see all colors? - Why are some sounds easier to hear than others?
2Sensation
- Sensation - the registration of physical stimuli
- Hearing - anatomy and function of the ear
- Vision - anatomy and function of the eye
- Psychophysics - the measurement of sensory
experiences
3Sensation
- What is the purpose of sensory processing?
- To transform physical stimuli in the environment
into neural signals in the brain - Example (Hearing) Sound waves are transformed
into vibrations in the ear, and the strength of
those vibrations are coded by sensory neurons
4Three Domains of Sensory Research
- Sensory Physiology
- Physiological Psychology
- Psychophysics
5Hearing Sound Waves
- Auditory perception occurs when sound waves
interact with the structures of the ear. - Sound Wave - changes over time in the pressure of
an elastic medium (for example, air or water). - Without air (or another elastic medium) there can
be no sound waves, and thus no sound
6Characteristics of Sound
- Frequency of a sound wave is related the pitch of
a sound - Amplitude of a sound wave is related to loudness
of a sound
7Frequency of Sound Waves
- The frequency of a sound wave is measured as the
number of cycles per second (Hertz) - 20,000 Hz Highest Frequency we can hear
- 4,186 Hz Highest note on a piano
- 1,000 Hz Highest pitch of human voice
- 100 Hz Lowest pitch of human voice
- 27 Hz Lowest note on a piano
8Intensity of Various Sounds
P (in sound- pressure units)
Example
Log P
Decibels
Softest detectable sound Soft whisper Quiet
neighborhood Average conversation Loud music from
a radio Heavy automobile traffic Very loud
thunder Jet airplane taking off Loudest rock band
on record Spacecraft launch 9from 150 ft.)
0 1 2 3 4 5 6 7 8 9
0 20 40 60 80 100 120 140 160 180
1 10 100 1000 10,000 100,000 1,000,000 10,000,000
100,000,000 1,000,000,000
9Intensity of Sound Waves
- The physical intensity of sound waves is measured
on the decibel (dB) scale - Intensity (in dB) 20 log (P/P0)
- P intensity of sound being measured
- P0 the lowest intensity 1,000 Hz tone we
can hear
10Anatomy of Ear
- Purpose of the structures in the ear
- Measure the frequency (pitch) of sound waves
- Measure the amplitude (loudness) of sound waves
11Major Structures of the Ear
- Outer Ear - acts as a funnel to direct sound
waves towards inner structures - Middle Ear - consists of three small bones (or
ossicles) that amplify the sound - Inner Ear - contains the structures that actually
transduce sound into neural response
12Anatomy of the Ear
13Anatomy of the Ear
14Transduction of Sounds
- The structures of the ear transform changes in
air pressure (sound waves) into vibrations of the
Basilar Membrane. - As the Basilar Membrane vibrates it causes the
hairs in the Hair Cells to bend. - The bending of the hairs leads to a change in the
electrical potential within the cell
15Coding of Sounds
The pattern of vibration along the Basilar
Membrane depends on the Frequency of the sound
wave
16Coding Sounds
- Low frequency sounds cause more vibration near
distal of Basilar Membrane - High frequency sounds cause more vibration near
proximal end of Basilar Membrane
17Coding and Auditory Masking
- The way in which waves travel down the Basilar
Membrane causes some sounds to interfere with (or
mask) our ability to hear other sounds - Low frequency sounds provide better masking than
high frequency sounds.
18Auditory Masking
- Low frequency sounds effectively mask high
frequency sounds - High frequency sounds can not effectively mask
low frequency sounds