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# The Hearing Process and Physics of Sound Study Notes

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Lecture 1
Objectives:
- Describe the physical bases of sound
- Identify the structures of the peripheral and central nervous system
- Describe the physiology of hearing
- Describe human perception of sound
- Three sections:
- Physics of sound
- Anatomy and physiology
- Psychoacoustics
The Hearing Process (general)
- Sound enters ear
- Coding occurs
- Processing ensues
- Integration of experience, processing, and other senses
- Response
Sound
- Sound is the result of vibrations
- Object must vibrate to produce or transmit sound
- Sound is defined by properties of
- Sound source→ where the sound comes from
- Transmitting medium→ surrounding air that transmits the sound
- Prerequisite for vibration:
- mass→ quantity of matter
- elasticity→ resistance to deformation; restoring force after deformation
Physics of sound I: Acoustics
- Sinusoids:
- Vibrations
- Frequency
- Phase
- Amplitude
- Vibration: simple harmonic motion
- Inertia→ ongoing motion
- First law: a body at rest will remain at rest or in uniform motion until acted upon
by an opposing force
- Elasticity (resistance to deformation; restoring force after deformation)
- Third Law: with every force there is an equal reaction force of opposite direction
- Parameters describing vibration
- amplitude→ maximum displacement
- frequency→ rate of vibration
- Starting Phase→ where does the vibration start?

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How do we get from simple harmonic motion to a sine wave?
- Amplitude: displacement over time
- Maximum→ the amplitude of the sine wave
- instantaneous→ any point in the sine wave that could be measured
- Sine waves can be measured in:
- Back to back movement
- Circular movement
- Sine ø = a / r (angle = height of triangle over radius)
- Called a sine wave because the position on the wave is determined by the sine of the
angle
RMS (root mean square) Amplitude:
- Square each instantaneous amplitude over one cycle average and take square root of that average
- RMS = √(sum of squared amplitudes/number of amplitudes)
- Ex question: sine wave has an amplitude of 2...
- .707 x peak amplitude (only for sine waves)
- .354 x peak-to-peak amplitude
Cycle Example:
- Frequency: 5Hz (5 cycles per second)
- Amplitude: 5
- Period: 200ms (how long it takes for the wave to complete once)
- ***As frequency increases, period decreases
- Formulas:
- F = 1/Pr
- Pr = 1/f
Wavelength and Frequency:
- Distance: As frequency increase, wavelength decreases
- Wl = c/f
- C = ~345 meters per second through air
- 1130 feet per second
- Speed of sound in water is 1500 m/s
- Speed of sound in steel is 6100 m/s
Phase:
- Two sound wave of same frequency starting at different phases: out of phase
- Two different sound waves starting together: in phase at start, out of phase for rest of time
Physics of Sound II
- Sound transmission
- Proagation
- Resonance
- Sound intensity
- decibels
- Interference
- Sound fields
Air Particle Movement = Sound Longitudinal

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Lecture 1 Objectives: - Describe the physical bases of sound - Identify the structures of the peripheral and central nervous system - Describe the physiology of hearing - Describe human perception of sound - Three sections: - Physics of sound - Anatomy and physiology - Psychoacoustics The Hearing Process (general) - Sound enters ear - Coding occurs - Processing ensues - Integration of experience, processing, and other senses - Response Sound - Sound is the result of vibrations - Object must vibrate to produce or transmit sound - Sound is defined by properties of - Sound source→ where the sound comes from - - Transmitting medium→ surrounding air that transmits the sound Prerequisite for vibration: - mass→ quantity of matter - elasticity→ resistance to deformation; restoring force after deformation Physics of sound I: Acoustics - Sinusoids: - Vibrations - Frequency - Phase - Amplitude - Vibration: simple harmonic motion - Inertia→ ongoing motion - - First law: a body at rest will remain at rest or in uniform motion until acted upon by an opposing force - Elasticity (resistance to deformation; restoring force after deformation) - Third Law: with every force there is an equal reaction force of opposite direction Parameters describing vibration - amplitude→ maximum displacement - frequency→ rate of vibration - Starting Phase→ where does the vibration start? How do we get from simple harmonic motion to a sine wave? - Amplitude: displacement over time - Max ...
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