Perry C Hanavan Au D Audiologist Civic Choir

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 l l l Nasty noises: Why do we recoil at unpleasant sounds? MOST UNPLEASANT SOUNDS Rating 74 sounds, people found the most unpleasant noises to be: 1. Knife on a bottle 2. Fork on a glass 3. Chalk on a blackboard 4. Ruler on a bottle 5. Nails on a blackboard 6. Female scream 7. Anglegrinder 8. Brakes on a cycle squealing 9. Baby crying 10. Electric drill LEAST UNPLEASANT SOUNDS 1. Applause 2. Baby laughing 3. Thunder 4. Water flowing

Sound l l vibration (movement) variation in sound pressure transmission through a medium (gas, liquid, solid) perceived by listener

How Do We Measure Pressure

Measurement: Pressure l l l Dynes Pounds per square inch microbar Pascal centimeters of water millimeters of mercury dyne/cm 2 psi bar Pa cm H 2 O mm Hg

Old vs. New Units of Measure Old New ---------------------dynes/cm 2 Pascal psi microbar

Metric System l l MKS cgs l http: //www. unc. edu/~rowlett/units/cgsmks. html http: //www. bipm. org/en/home/ l Metric System Rap l

Pressure at different locations may vary l l l P atmos P pos P neg P oral P trach P alveolar

Air (gas) l l consists of molecules Brownian motion governed by predictable laws equal dispersion throughout area

Air Movement l l 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

Air Pressure, Volume, Density l l l 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

Air Pressure Changes from Sound l l Condensation Rarefaction Soundry Sound wave applet Amplitude Peak amplitude Wavelength Period

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

Forces of Sound l l Inertia – body in motion Elasticity – restoring force Newton’s Cradle

Hooke’s Law l l l l 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 You. Tube video of Hooke’s Law You. Tube video of vibrating vocalis muscles

Components of Sound Wave l l 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 l l l l 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] [mp 3] Risset continuous change [wav] [mp 3]

Pure Tone/Sine Wave/Sinusoidal

Waveforms & Line Spectrums

Waveforms & Envelopes

Length/Mass/Tension and Frequency l Length l Mass l Tension

Phase

Interference l l l Constructive Destructive Fourier analysis

Sound Waves l l Simple Complex Periodic l l Fundamental Harmonics Complex Aperiodic

Waveforms and Spectra l Fourier Analysis of waveforms

Damped Waveforms

Psychoacoustics l l l Intensity (d. B) Frequency (Hz) Time Loudness (phons) Pitch (mels) Duration

Resonance l l Natural frequency Resonant frequency Mechanical Acoustic

Resonate a Wine Goblet l l You. Tube 1 You. Tube (Mythbusters)

Resonators as Filters l Bandwidth l Regularly shaped acoustic resonator l l Irregularly shaped acoustic resonator l l l Broadly tuned and heavily damped Cutoff frequencies Resonance curves Center frequency Types of filters l l Narrowly tuned and lightly damped 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

Question Which instrument would be more finely tuned? A. Flute B. Tuba C. Saxophone D. French horn

Narrow vs. Broad Filter

Question What do we consider the upper and lower cutoff frequency? A. 6 d. B down from center frequency B. 3 d. B down from center frequency C. 5 d. B down from center frequency D. 9 d. B down from center frequency

Filters - Bandpass

Filters l Low pass filters (cut the high frequencies) High pass filters (cut the low frequencies) Band pass filters (cut high and low) l You. Tube filters l l

Passband Resonator

Bandpass Filter l Filter Simulation

Bandpass Tubing/Hearing Aids l High Bandpass earmold tubing l Low Bandpass earmold tubing

Bandpass/Earhooks l High and Low Pass Filters

Bandpass/Speech Mechanism l Modeling Speech

Question 600, 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 Hz