Chapter 2: Sound

sound pulses created by a transducer travel through biological tissue, or ____

media

all waves carry ____ from one location to another

energy

sound is a ____ wave in which particles in the medium move

mechanical

sound travels through a medium, where molecules are alternately ____ and ____

compressed; rarefied

squeezed together

compressed

stretched apart

rarefied

sound travels in a ____ line

straight

sound waves are ____ waves

longitudinal

the effect of the medium upon the sound wave

acoustic propagation properties

the effects of the sound wave upon the biologic tissue through which it passes

biologic effects

three acoustic variables are used to distinguish between sound waves and other types of waves

pressure, density, and distance

sound waves are also known as ____ waves

acoustic

concentration of force in an area

pressure

units of pressure

pascals (Pa)

concentration of mass in a volume

density

units of density

kg/cm³

measure of particle motion

distance

units of distance

cm, feet, mile

there are ____ acoustic parameters

seven

the seven acoustic parameters:

• period

• frequency

• amplitude

• power

• intensity

• wavelength

• propagation speed

in a ____ wave, particles move in a direction that is perpendicular (at right angles) to the direction that the wave propagates

transverse

in a ____ wave, particles move in the same direction that the wave propagates

longitudinal

a pair of waves are considered ____ when their peaks (max values) occur at the same time and at the same location and troughs of the waves (min values) occur at the same time and place

in-phase

when two waves are ____, their peaks occur at different times, and so do their troughs: they are “out of step”

out-of-phase

multiple beams may arrive at an identical location at exactly the same time and the waves lose their individual characteristics at that moment and combine to form a single wave

interference

type of interference of in-phase waves results in formation of a single wave of greater amplitude than either of its components

constructive interference

type of interference of out-of-phase waves results in formation of a single wave of lesser amplitude than at least one of its components

destructive interference