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
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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...