Transcript Slides

Corbett Griffith, Designer
Corbett Griffith founded Instinct after
attending Georgia Tech and
graduating at the top of his class
in Mechanical Engineering with a
minor in Sculpture, from Georgia
State.
Since childhood, he's been
deconstructing or tearing apart
things only to replace them with a
creation to be admired.
John McClusky, Designer
Professor John McClusky is an
Industrial Designer at SJSU. He has
provided product design, design
research, human factors consulting,
and strategic planning for Xerox and
Fuji Xerox, Swingline/Acco Brands,
Herman Miller, Proctor & Gamble,
Whirlpool, and Rio Digital Audio.
Prof. McClusky
did the grading of
your egg package
designs
The Ear & The Brain
Waves
Concept of vibrations extends into the
phenomenon of wave motion.
String
Sound
Water waves
Radio
Light waves
Doing “The Wave”
Synchronized standing and
sitting by a stadium’s crowd is
an example of a transverse
wave.
Video analysis indicates that it takes only a few
dozen fans leaping to their feet with their arms up
to trigger a wave. Once started, it usually rolls in
a clockwise direction at a rate of about 40 feet
per second, or about 20 seats per second. At any
given time, the wave pulse is about 15 seats
wide.
Demo: Sound is not Wind
With sound, air molecules oscillate in place.
With wind, air moves from place to place.
Smoke rings are not
sound because the
air moves from
place to place.
Media That Transmit Sound
Sound travels better
through elastic liquids
and solids, such as
water and rocks, than
through air.
This is due to the close
proximity of the atoms
as they vibrate.
Hear richer, louder
sound transmitted
by string
What Your Voice Sounds Like
Your voice sounds different
to you when you hear it
from a recording.
This is because when you
are speaking aloud, most
sound waves reach your
ear traveling through the
solid flesh and bone of
your skull.
Leave yourself
a voice-mail
Transverse Waves
For transverse waves the wave’s amplitude
is perpendicular to the wave’s motion.
Amplitude
Wave Motion
Amplitude
Longitudinal Waves
For longitudinal waves, amplitude and wave
motion are parallel.
Wave Motion
Amplitude
Amplitude
Nature of Sound in Air
Sound in air is a longitudinal wave created
by compressions and rarefactions.
Wavelength
Wavelength is distance between crests or
between troughs of waves.
Standing Waves
When a wave interferes with its reflection,
this may create a standing wave.
Standing Waves & Phase
Playing Brass Instruments
Depending on how the musician blows into the mouthpiece,
different standing waves of different frequencies (different
notes) are produced.
Fundamental & Overtones
The Fundamental is the lowest frequency standing wave.
The Overtones are twice, three times, etc., the frequency of
the Fundamental.
110 Hz (A2)
220 Hz (A3)
330 Hz (E4)
Frequencies of standing waves for a pipe that is 151 cm long
Harmonic Series
Music for natural horns and bugles is limited
by harmonic series, the frequencies of the
fundamental and overtones.
Fundamental
Changing the Length
To play notes beyond the harmonic series
requires changing the frequency of the
fundamental by changing the length of tube.
Crooks
Finger-holes
Cornett
Disadvantage: Reduced amplitude
Disadvantage: Clumsy
Changing the Length
Trombone uses a continuous slide to vary its length
Cornett
Changing the Length
Valves used in trumpet, tuba, and French horn
Cornett
Similar to using a crook but easy to open & close
Speed of Sound in Air
Speed of sound in air
is about 340 m/s.
Sound travels about
one kilometer in
three seconds,
about one mile in
five seconds.
Light is a million times
faster than sound.
Wave Speed
The speed at which waves travel is called
the wave speed.
Speed of sound = 330 m/s = 725 mi/hr
Speed of light = 300,000,000 m/s
Wave Relations
Wave speed, wavelength & frequency related.
(Wave speed) = (Wavelength) x (Frequency)
(Wave speed)
(Wave length) =
(Frequency)
(Wave speed)
(Frequency) =
(Wavelength)
Demo: Helium Voice
Sound speed in helium is
higher than speed in air.
Wavelength of sound
unchanged (size of vocal
cords is unchanged).
Frequency of voice is higher
since
(Wave speed)
(Frequency) =
(Wavelength)
Breath Helium…
He
Talk like me!
Human Ear
Pressure variations of sound waves push the eardrum, whose vibrations
are transmitted by the ossicles (ear bones) to the cochlea (hearing canal)
Cochlea
Vibrations transmitted by the ear bones create oscillations
in the fluid with the cochlea (snail in Latin), which is a
spiral-wrapped tube.
These oscillations within the cochlea cause the basilar
membrane to ripple, like a waving flag.
Organ of Corti
The organ of Corti forms a ribbon of sensory epithelium
that runs lengthwise down the entire cochlea.
The hair cells of the organ of Corti selectively transform the
oscillations of the basilar membrane into nerve signals.
Demo: Hearing Sound
Different frequencies stimulate different groups of
hair cells depending on the resonance region on
the basilar membrane.
Range of human hearing is roughly 20 Hertz to
20,000 Hertz.
Hearing in Animals
Frequency range varies widely, depending on natural adaptation
using sound to communicate, locate food, avoid predators, etc.
Loudness & Amplitude
Loudness depends on amplitude of pressure
and density variations in sound waves.
Loudness
Loudness of sound depends on
the amplitude of pressure
variations in the sound waves.
Loudness is measured in decibels (dB),
which is a logarithmic scale (since our
perception of loudness varies
logarithmically).
From the threshold of hearing (0 dB) to the
threshold of pain (120 dB) the pressure
increase is a million times higher.
At the threshold of pain (120 db) the
pressure variation is only about 10 Pascals,
which is one ten thousandths atmospheric
pressure.
Amplitude & Frequency
Perceived loudness contours for various frequencies and amplitudes
Low frequency and very high frequency sound requires high amplitude to be heard
Hearing by Age & Sex
Absolute thresholds of hearing by age in males and females
Male, Age 60
Male, Age 50
Female, Age 60
Male, Age 40
Male, Age 30
Male, Age 20
Hearing acuity decreases with age, especially in the high frequencies.
In general, women have greater acoustic sensitivity than men.
Hearing Loss
The hair cells that line the cochlea are a delicate and
vulnerable part of the ear. Repeated or sustained
exposure to loud noise destroys the neurons of the
Organ of Corti.
Once destroyed, the hair cells are not replaced, and the
sound frequencies interpreted by them are no longer
heard.
Hair cells that respond to high
frequency sound are very
vulnerable to destruction, and
loss of these neurons typically
produces difficulty understanding
human voices.
Much of this type of permanent
hearing loss is avoidable by
reducing exposure, such as to
loud music.
What?