Acoustics Chapter 1
Terms
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 Wave
 a disturbance traveling in an elastic medium
 Types of waves:
 Transverse, longitudinal, sinusoidal, and impulsive
 Longitudinal wave

waves in which the particles in the medium move parallel to the direction in which the wave itself travels. Ex.
sound waves & slinky  Sinusoidal wave
 are oscillatory wave shapes that have a special simple shape like a mathematical sine or cosine curve. smooth undulating shape
 Impulsive wave

made up of a single burst of one or several pulses. Ex.
a bang noise, like clapping your hands.  Oscillatory waves
 wave shapes that always have a repeating pattern
 Propagation velocity (or wave velocity)
 the speed at which something moves along a wave
 Speed
 distance divided by time
 Medium velocity
 the speed with which a point of the medium moves as the wave passes that point
 Five properties of waves:
 wavelength, cycle, period, amplitude, and frequency
 wavelength
 the distance from one peak of the wave to the next adjacent peak. The distance a wave moves in one period.
 cycle
 a complete round trip of point B from its original position, up, down all the way to its lowest position, and back to its original
 period (T)
 the time required to complete one cycle (time per cycle)
 amplitude (A)
 the maximum distance that point B is displaced from its normal nonvibrating position. amplitude is the maximum value of the displacement.
 frequency (f)

the number of cycles per second of time. Usually referred to in Hertz (Hz). Ex. 2 cycles per second =
2 Hz  Displacement
 the distance that point B (or other point) is moved from its normal nonvibrating position. (the position when there is no wave)
 Wave (or propagation) velocity
 the speed with which a crest or any other part of the wave moves in the direction of the wave
 Pitch
 sensation of different sounding frequencies. The greater the frequency, the higher the pitch.
 Pure tone
 vibrations that occur at the same frequency
 Mass
 a measure of the amount of material in a body
 Inertia
 the tendency of a body to remain in its present state of motion. if at rest, a body will stay at rest unless there is a force to get it moving. if it is in motion, a force is required to make it move faster/slower
 Friction
 a force caused by the surface roughness of two objects in contact when one object moves relative to the other.
 pressure

force per unit area.
pounds per square inch or
Newtons per square meter  Pascals
 Newtons per square meter