1. 1 Sensation and Perception zIn this part of the course we will try to answer such questions as: yHow do we see and hear? yWhy does a TV only need three phosphors (Red, Green and Blue) to allow us to see all colors? yWhy are some sounds easier to hear than others?

2. 2 Sensation zSensation - the registration of physical stimuli yHearing - anatomy and function of the ear yVision - anatomy and function of the eye yPsychophysics - the measurement of sensory experiences

3. 3 Sensation zWhat is the purpose of sensory processing? yTo transform physical stimuli in the environment into neural signals in the brain yExample (Hearing): Sound waves are transformed into vibrations in the ear, and the strength of those vibrations are coded by sensory neurons

4. 4 Three Domains of Sensory Research zSensory Physiology zPhysiological Psychology zPsychophysics Sensory experiencePhysical stimulus Domain of Sensory physiology Domain of sensory psychophysics Domain of sensory physiological psychology Physiological response

5. 5 Hearing: Sound Waves zAuditory perception occurs when sound waves interact with the structures of the ear. zSound Wave - changes over time in the pressure of an elastic medium (for example, air or water). zWithout air (or another elastic medium) there can be no sound waves, and thus no sound

6. 6 Characteristics of Sound zFrequency of a sound wave is related the pitch of a sound zAmplitude of a sound wave is related to loudness of a sound Greatest compression of molecules Least compression of molecules One cycle Amplitude Higher amplitude (Louder) Lower amplitude (Softer) Higher frequency (Higher pitch) Lower frequency (Lower pitch) (a) (b)

7. 7 Frequency of Sound Waves zThe frequency of a sound wave is measured as the number of cycles per second (Hertz) y20,000 HzHighest Frequency we can hear y 4,186 HzHighest note on a piano y 1,000 HzHighest pitch of human voice y 100 HzLowest pitch of human voice y 27 HzLowest note on a piano

8. 8 Intensity of Various Sounds Example P (in sound- pressure units) Log PDecibels 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.) 1 10 100 1000 10,000 100,000 1,000,000 10,000,000 100,000,000 1,000,000,000 01234567890123456789 0 20 40 60 80 100 120 140 160 180

9. 9 Intensity of Sound Waves zThe physical intensity of sound waves is measured on the decibel (dB) scale yIntensity (in dB) = 20 log (P/P 0 ) yP = intensity of sound being measured yP 0 = the lowest intensity 1,000 Hz tone we can hear

10. 10 Anatomy of Ear zPurpose of the structures in the ear: yMeasure the frequency (pitch) of sound waves yMeasure the amplitude (loudness) of sound waves

11. 11 Major Structures of the Ear zOuter Ear - acts as a funnel to direct sound waves towards inner structures zMiddle Ear - consists of three small bones (or ossicles) that amplify the sound zInner Ear - contains the structures that actually transduce sound into neural response

12. 12 Anatomy of the Ear Pinna Sound waves Auditory Canal- Stirrup Cochlea Auditory nerve Semicircular canals Round window Oval window Where stirrup attaches Eardrum (tympanic Membrane) Bone Hammer Anvil

13. 13 Anatomy of the Ear Outer earMiddle earInner ear A sound causes the basilar membrane to wave up and down. Basilar membrane Hair cells Tectorial membrane Round window Eardrum Oval window Cochlea, partially uncoiled Stirrup Anvil Hammer Sound waves Auditory canal

14. 14 Transduction of Sounds zThe structures of the ear transform changes in air pressure (sound waves) into vibrations of the Basilar Membrane. zAs the Basilar Membrane vibrates it causes the hairs in the Hair Cells to bend. zThe bending of the hairs leads to a change in the electrical potential within the cell

15. 15 Coding of Sounds The pattern of vibration along the Basilar Membrane depends on the Frequency of the sound wave Basilar membrane Distal end Proximal end Oval window Direction of traveling wave

16. 16 Coding Sounds zLow frequency sounds cause more vibration near distal of Basilar Membrane zHigh frequency sounds cause more vibration near proximal end of Basilar Membrane Piccolo, soft Bassoon, loud Piccolo, loud Bassoon, soft Distance along basilar membrane (a) Distance along basilar membrane (b) Effect of bassoon on basilar membrane Vibration amplitude of basilar membrane Vibration amplitude of basilar membrane Effect of piccolo on basilar membrane

17. 17 Coding and Auditory Masking zThe way in which waves travel down the Basilar Membrane causes some sounds to interfere with (or mask) our ability to hear other sounds zLow frequency sounds provide better masking than high frequency sounds.

18. 18 Auditory Masking zLow frequency sounds effectively mask high frequency sounds zHigh frequency sounds can not effectively mask low frequency sounds Piccolo, soft Bassoon, loud Piccolo, loud Bassoon, soft Distance along basilar membrane (a) Distance along basilar membrane (b) Effect of bassoon on basilar membrane Vibration amplitude of basilar membrane Vibration amplitude of basilar membrane Effect of piccolo on basilar membrane