PH 105 Dr. Cecilia Vogel Lecture 8
OUTLINE Exam #1 Hearing subjective qualities of sound the ear intensity vs pressure pressure and frequency sensitivity
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
Subjective Qualities of Sound: Loudness Pitch Timbre tone quality (Subjective) duration
Hearing Relating physical and subjective properties: LoudnessPitchTimbreDuration *Amplitude*Frequency*Spectrum*Duration
Outer Ear Pinna helps collect sound like satellite dish collects radio waves helps determine Auditory canal tube. helps sound
Middle Ear Pressure wave from outer ear has energy = vibrates eardrum which moves the ossicles (______) which exert pressure on
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
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
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
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
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