1. PH 105 Dr. Cecilia Vogel Lecture 8

2. OUTLINE  Exam #1  Hearing  subjective qualities of sound  the ear  intensity vs pressure  pressure and frequency sensitivity

3. Physical properties of sound  amplitude, intensity  amplitude =  intensity = energy in wave/area/time  demos: intensity of light depends on energy/time and energy/area  intensity of sound proportional to pressure amplitude squared  frequency =  spectrum  which pure tone freq’s are present & at what level  envelope  how amplitude varies with  duration

4. Subjective Qualities of Sound:  Loudness  Pitch  Timbre  tone quality  (Subjective) duration

5. Hearing  Relating physical and subjective properties: LoudnessPitchTimbreDuration *Amplitude*Frequency*Spectrum*Duration

6. Outer Ear  Pinna  helps collect sound  like satellite dish collects radio waves  helps determine  Auditory canal  tube.  helps sound

7. Middle Ear  Pressure wave from outer ear  has energy =  vibrates eardrum  which moves the ossicles (______)  which exert pressure on

8. Ossicle Physics  Pressure =  Pressure can be increased by  decreasing the area (knife edge)  round window of inner ear has 20X _______ area than eardrum  increasing the force (leverage)  ossicles act as a small force large lever arm large force

9. Inner Ear  Vibration in middle ear  creates pressure wave in cochlear fluid in  which vibrates the basilar membrane  stiff part resonates at  helps us determine stiffer less stiff basilar membrane  vibrations in basilar membrane bend  which send nerve signals to

10. Limits of Hearing  The ear is sensitive to large range of pressure amplitudes  pressure variations as low as about ________ N/m 2 can be heard  compare to ______ N/m 2 atmospheric pressure  pressure variations as high as about _____ N/m 2 can be heard without pain  1/1000 atmospheric pressure  The ear is sensitive to large range of frequencies  from about ___ Hz to about ___ __Hz  more sensitive in

11. Critical Bands  Basilar membrane vibration helps us determine  If two sounds have similar basilar membrane response  they are said to lie within a critical band  Size of critical band is about 4 semitones for range of freq’s used in music  the size of the critical bands is larger at   Just noticeable difference

12. Summary  Subjective qualities of sound do not have direct correlation to physical properties  Mostly: loudness/amplitude, pitch/frequency, timbre/spectrum, subjective duration/duration  Outer ear collects and amplifies  In middle ear, ossicles increase the pressure  Inner ear fluid vibrates membrane, which sends nerve signal to brain  Ear is sensitive to large range of pressure and frequency