Perry C. Hanavan, Au.D.

Audiologist

Civic Choir

Parody

If a tree falls in the forest, and no one hears it, will there be a sound?...

If a tree falls in the forest, and no one hears it, will there be a sound?...This is an old philosophical dilemma which relies on using the word "sound" for two different purposes. One use is as a description of a particular type of physical disturbance:

"Sound is an organized movement of molecules caused by a vibrating body in some medium - water, gas, solid or whatever."

The other is as a description of a sensation: "Sound is the auditory sensation produced through the ear by the alteration ... in pressure, particle displacement, or particle velocity which is propagated in an elastic medium."

Both definitions are correct, they differ only in the first being a cause and the second being an effect.

Sound saturates the environment

Nasty Noises

Nasty noises: Why do we recoil at unpleasant sounds?

MOST UNPLEASANT SOUNDSRating 74 sounds, people found the most unpleasant noises to be:1. Knife on a bottle2. Fork on a glass3. Chalk on a blackboard  4. Ruler on a bottle5. Nails on a blackboard6. Female scream7. Anglegrinder8. Brakes on a cycle squealing9. Baby crying10. Electric drill

LEAST UNPLEASANT SOUNDS1. Applause2. Baby laughing3. Thunder4. Water flowing

Sound

vibration (movement) variation in sound

pressure transmission through

a medium (gas, liquid, solid)

perceived by listener

How Do We Measure Pressure

Measurement: Pressure

Dynes dyne/cm2

Pounds per square inch psi microbar bar Pascal Pa centimeters of water cm H2O millimeters of mercury mm Hg

Old vs. New Units of Measure

Old New

-------------------------------------------

dynes/cm2 Pascal

psi microbar

Metric System

MKS cgs

http://www.unc.edu/~rowlett/units/cgsmks.html http://www.bipm.org/en/home/

Metric System Rap

Pressure at different locations may vary

P atmos

P pos

P neg

P oral

P trach

P alveolar

Air (gas)

consists of molecules Brownian motion governed by predictable laws equal dispersion throughout area

Air Movement driving pressure: (difference

in pressure) high pressure FLOWS to low pressure and low pressure FLOWS to high pressure areas

volume velocity: rate of flow laminar flow: flow in a

parallel manner turbulent flow: non-parallel

manner (flows around an object)

Question

Boyle’s Law deals with?

A. Gravity

B. Force

C. Pressure changes with volume

D. Temperature

E. I don’t know SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...

Air Pressure, Volume, Density

Volume: amount of space in three dimensions

Density: amount of mass per unit of volume

Boyle’s laws: as volume decreases, pressure increases

Question

A condensation is?

A. Positive air pressure area

B. Negative air pressure area

C. Less molecules than other areas

D. “Rain Drops Keep Falling on My Head”

E. Speaking down to people SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...

Air Pressure Changes from Sound

Condensation Rarefaction

Soundry

Sound wave applet

Amplitude

Peak amplitude

Wavelength

Period

Propagation of Sound

Condensations Rarefactions

Example of molecular motion Components of sinusoid Parts of a wave Transverse wave simulation Applet: Square, triangle, simulation Various Sound applets

Forces of Sound

Inertia – body in motion Elasticity – restoring force

Newton’s Cradle

Hooke’s Law

Law of elasticity is an approximation that states that the extension of a spring is in direct proportion with the load applied to it.

Many materials obey this law as long as load does not exceed material's elastic limit called "Hookean" materials

Hookean materials: broad term including mechanics of vocalis muscles.

Hooke's law in simple terms says that stress is directly proportional to strain.

Mathematically, Hooke's law states that: F= -kx YouTube video of Hooke’s Law YouTube video of vibrating vocalis muscles

Components of Sound Wave

Amplitude Frequency – number of cycles per second Period – time to complete one cycle Wavelength – distance traveled in one cycle

Pendulum Simulation

Sounds in Air Sims

Examples

Piano Note Timbre Physics of Sound The Missing Fundamental Effect Pitch as a linear scale Octave effect Piano Octaves Pitch as a helix Pitch chroma circle Shepard tone Endless staircase - visual illusion Endless staircase - Shepard illusion Shepard discrete steps [wav] [mp3] Risset continuous change [wav] [mp3]

Pure Tone/Sine Wave/Sinusoidal

Waveforms & Line Spectrums

Waveforms & Envelopes

Length/Mass/Tension and Frequency

Length

Mass

Tension

Phase

Interference

Interference Constructive Destructive

Fourier analysis

Sound Waves

Simple Complex Periodic

Fundamental Harmonics

Complex Aperiodic Aperiodic

Waveforms and Spectra

Fourier Analysis of waveforms

Damped Waveforms

Psychoacoustics

Intensity (dB) Loudness (phons) Frequency (Hz) Pitch (mels) Time Duration

Resonance

Natural frequency Resonant frequency

Mechanical Acoustic

Resonate a Wine Goblet

YouTube 1 YouTube (Mythbusters)

Resonators as Filters

Bandwidth Regularly shaped acoustic resonator

Narrowly tuned and lightly damped Irregularly shaped acoustic resonator

Broadly tuned and heavily damped Cutoff frequencies Resonance curves Center frequency Types of filters

Low pass High pass Band pass

Low/High Pass Filter Example (on computer)

Resonators

Acoustic Resonators/Bandwidth

Question

Is the human vocal tract:

A. A regularly shaped tube

B. An irregularly shaped tube

SMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...

Question

Which instrument would be more finely tuned?

A. Flute

B. Tuba

C. Saxophone

D. French hornSMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...

Narrow vs. Broad Filter

Question

What do we consider the upper and lower cutoff frequency?

A. 6 dB down from center frequency

B. 3 dB down from center frequency

C. 5 dB down from center frequency

D. 9 dB down from center frequencySMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...

High Band Pass Filters

Filters

Low pass filters (cut the high frequencies) High pass filters (cut the low frequencies) Band pass filters (cut high and low)

YouTube filters

Passband Resonator

Bandpass Filter

Filter Simulation

Bandpass Tubing/Hearing Aids

High Bandpass earmold tubing

Low Bandpass earmold tubing

Bandpass/Earhooks

High and Low Pass Filters

Bandpass/Speech Mechanism

Modeling Speech

Question600, 900, 1200 Hz

What is the missing fundamental in this example?

A. 30 Hz

B. 60 Hz

C. 100 Hz

D. 200 Hz

E. 300 HzSMART Response QuestionTo set the properties right click and selectSMART Response Question Object->Properties...