Ch 1 (MIDTERM) Flashcards
Density
How packed atoms are
m/v
Inertia
Newton’s first law of motion
Every object in motion remains in motion unless an external force is applied to it
Friction
Resistance, constant for all frequencies
Elasticity
Stiffness, how well an object resists compression, change
Boyle’s Law
Pressure and volume have inverse relationship, has a lot to do with aspiration
3 things needed for sound
Energy Source
Body that can vibrate
Medium
Nature of sound
Sound is caused by a change in air pressure by a disturbance.
Disturbance is caused by movement (vibration) of an object
Movement causes pressure change in medium (Compression/ Rarefaction)
Pressure change in medium moves ear structures -> audible sound
Ranges of Human hearing
20-20,000 Hz
250-8,000Hz for speech sounds
Bell & Hammer Analogy
When struck, bell vibrates (disturbance)
Compression: Bell pushes away from hammer, and pushes air molecules together (more dense, more pressure)
Rarefaction: Bell is pulled back due to elasticity, empty space filled with air particles again
(less dense, less pressure)
Brownian Motion
Random 3D movement of air particles
Constant motion, wants to “fill” in empty spaces
Sound is basically…
Change in air pressure caused by a disturbance
NOT the same air molecule traveling, but the change in air pressure is what propagates and reaches you
Behavior of air
Closer/dense = more collisions= more pressure
Force of pressure moves eardrums
Sound is longitudinal (parallel to direction of wave)
Elasticity and Intertia play-off
Elasticity Reigns in
Inertia overshoots
same applies to the air particle (imagine pendulum)
Dampening
Caused by friction/air resistance, eventually lessens the vibrations
Inertia’s overshooting allows sound to continue with reapplying force continuously
What is 1 full cycle?
One full compression, one full rarefaction
Must start and end at the same place
