Chapter 3

Question 0

Compressions

Answer 0

Areas of increased pressures or density

Question 1

Sound waves

Answer 1

Carries energy
Created by vibration of moving object
Must travel through medium
Series of compressions and rarefactions

Question 2

Rarefactions

Answer 2

Areas of decreased pressure or density

Question 3

Acoustic parameters (7)

Answer 3

Amplitude
Period
Frequency
Power
Intensity 
Speed
Wavelength

Question 4

Period

Answer 4

Time for one wave to vibrate single cycle

Measured in units of time

Determined by source
Not adjustable

Question 5

Frequency

Answer 5

Number of cycles in one second

Measured in Hz

Determined by source

Not adjustable

Question 6

Clinical frequency range

Answer 6

2 MHz - 15 MHz

Question 7

Frequency equation

Answer 7

F = #cycles / period

Frequency and period are reciprocals

Question 8

Source

Answer 8

The ultrasound system and transducer

Question 9

Medium

Answer 9

Material or tissue that sound travels through

Question 10

Human hearing range

Answer 10

20 Hz - 20 kHz (20,000 Hz)

Question 11

Infrasound

Answer 11

Frequency below 20 Hz

Question 12

Ultrasound

Answer 12

Sound greater than 20 kHz

Question 13

Bigness parameters

Answer 13

Amplitude
Power
Intensity

Question 14

Amplitude

Answer 14

Peak variation of a wave above or below baseline

Measured in dB

Determined by source
Adjustable via control

Question 15

Units of acoustic variables

Answer 15

Pressure - pascals
Density - g/cm cubed
Particle motion distance - cm, inches

Question 16

Amplitude ranges

Answer 16

1 MPa - 3 MPa

Question 17

Amplitude equation

Answer 17

Amplitude = (min - max) / 2

Question 18

Power

Answer 18

Rate of energy transfer or work done

Measured in watts

Determined by source

Adjustable with control

Question 19

Power clinical values

Answer 19

.004 - .090 watts

Question 20

Power equation

Answer 20

Power = amplitude squared

Question 21

Intensity

Answer 21

Concentration of energy in a sound beam
Measured as W/square cm
Determined by source, but changes as beam propagates or if beam shape is adjusted
Adjustable

Question 22

Intensity clinical values

Answer 22

0.01 -300 W/cm squared

Question 23

Wavelength

Answer 23

Distance of one complete cycle

Measured in units of distance (mm, cm)

Determined by source and medium

Not adjustable

Question 24

Clinical wavelength range

Answer 24

0.1 - 0.8 mm

Question 25

Wavelength equation

Answer 25

Wavelength = v / f ``` v = velocity f = frequency ``` Wavelength is inversely related to frequency

Question 26

Soft tissue wavelength

Answer 26

1.54 km/s Or 1540 m/s

Question 27

Propagation speed

Answer 27

Distance sound wave travels through a medium in 1 sec Measured in m/s (distance/time) Affected only by medium

Question 28

Clinical speed ranges

Answer 28

500 - 4000 m/s Depends on type of tissue

Question 29

Propagation speed equation

Answer 29

Wavelength = prop speed/frequency Or Distance traveled/time it took

Question 30

Stiffness

Answer 30

Ability of an object to resist compression or a mediums ability to be moved Directly related to speed Increased stiffness = increased speed

Question 31

Density

Answer 31

How closely packed a mediums molecules are Inversely related to speed