Chapter 2: sound Flashcards
what kind of wave is sound?
mechanical
what does compressed mean? rarefied?
squeezed together; stretched apart
how does sound travel?
in a straight line
sound waves are ____________ waves
longitudinal
what are acoustic propagation properties?
Effects of the medium upon the sound wave
what are biologic effects?
the effects of the sound wave upon the biologic tissue through which it passes
sound waves are aka what? how are these identified?
acoustic waves; identified by oscillations in acoustic variables
what are the 3 acoustic variables?
pressure, density, distance
what is pressure? units?
conc of force in an area; pascals (Pa)
what is density? units?
conc of mass in a volume; kg/cm^3
what is distance? units?
measure of particle motion; cm, feet, mile
what is used to describe the characteristics of a sound wave?
acoustic parameters
what are the 7 acoustic parameters?
period, frequency, amplitude, power, intensity, wavelength, propagation speed
how do the particles move in a transverse wave?
perpendicular (right angles) to the direction that the wave propagates. (ex: wave moves left to right particles in the wave move up and down)
how do particles move within a longitudinal wave?
in the same direction that the wave propagates (ex: wave moving left to right, particles in the wave move left to right)
are sound waves transverse or longitudinal?
longitudinal
when would a pair of waves be considered in-phase?
when their peaks (max value) and troughs (min value) occur at the same time and location
when would a pair of waves be considered out-of-phase?
their peaks/troughs occur at different times (out of step)
what is interference?
when multiple sound beams arrive at an identical location at exactly the same time. The waves lose individual characteristics and combine to form a single wave.
do in-phase or out-of-phase waves combine to create interference?
both
what is constructive interference? what waves make this up?
interference of in-phase waves creating a single wave of greater amplitude than either of its components
what is destructive interference? Which waves make this up?
interference of a pair of out-of-phase waves resulting in the formation of a single wave of lesser amplitude than at least one of its components
what happens when two out-of-phase waves are of equal amplitude?
complete destructive interference; they cancel each other out
what happens when waves of different frequencies interfere?
at some point the waves are in phase and the interference is constructive at another point the waves are out of phase and interference is destructive; both constructive and destructive interference occur
