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.

Water waves

Light waves

Sound

Radio

String

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

Wave Motion

Transverse Waves

For transverse waves the wave’s amplitude is perpendicular to the wave’s motion.

Amplitude

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 & OvertonesThe 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

Finger-holes

Disadvantage: Reduced amplitude

Cornett

Crooks

Disadvantage: Clumsy

To play notes beyond the harmonic series requires changing the frequency of the fundamental by changing the length of tube.

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 length) =

(Frequency) =

(Wave speed)

(Frequency)

(Wave speed)(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

He

Talk like me!

(Wave speed)(Wavelength)(Frequency) =

Breath Helium…

Human Ear

Pressure variations of sound waves push the eardrum, whose vibrations are transmitted by the ossicles (ear bones) to the cochlea (hearing canal)

CochleaVibrations 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.

LoudnessLoudness 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

Low frequency and very high frequency sound requires high amplitude to be heard

Perceived loudness contours for various frequencies and amplitudes

Hearing by Age & Sex

Hearing acuity decreases with age, especially in the high frequencies.In general, women have greater acoustic sensitivity than men.

Absolute thresholds of hearing by age in males and females

Male, Age 20

Male, Age 30

Male, Age 40

Male, Age 50

Male, Age 60

Female, Age 60

Hearing Loss

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.

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.

What?