Transcript A Brief History of Planetary Science

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:
Loudness
Pitch
Timbre
Duration
*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)
large force
ossicles act as a
small 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/m2 can be heard
compare to ______ N/m2 atmospheric pressure
pressure variations as high as about _____
N/m2 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