Chapter Two - Sound

Question 1

Macro means what?

Answer 1

Bigger

Question 2

The effects of the soundwave on biological tissue?

Answer 2

Biologic effects

Question 3

The effects of the medium on the soundwave?

Answer 3

Acoustic propagation properties

Question 4

What is sound?

Answer 4

A type of wave that carries energy place to place

Question 5

What does sound have to have to travel?

Answer 5

A medium

Question 6

What identifies which waves are sound waves?

Answer 6

Acoustic variables

Question 7

What are the acoustic variables?

Answer 7

Pressure, density, distance

Question 8

What is the units for pressure?

Answer 8

Pascals (Pa)

Question 9

What is pressure?

Answer 9

Force/area

Concentration of force within an area

Question 10

What are the units for density? What is the definition of density?

Answer 10

kg/centimeters cubed.

Concentration of mass within a volume

Question 11

What are compressions?

Answer 11

Regions of higher pressure and density

Question 12

What are rarefactions?

Answer 12

Regions of lower density and pressure

Question 13

What identifies which waves are sound waves?

Answer 13

Acoustic variables

Question 14

What describes the features of a particular sound wave?

Answer 14

Acoustic parameters

Question 15

What are the units for period?

Answer 15

Micro seconds or any unit of time

Question 16

What are the typical ultrasound values for PERIOD?

Answer 16

0.06–0.5 µs

Question 17

PERIOD is determined by what? Can PERIOD be changed by the sonographer?

Answer 17

Sound source

No

Question 18

What is the definition of PERIOD?

Answer 18

Time required to complete a single cycle.

Question 19

Is circumference length or area?

Answer 19

Length

Question 20

Define frequency.

Answer 20

The frequency of a wave is the number of cycles of an acoustic variable that occur in one second

Question 21

Units of frequency?

Answer 21

Per second, 1/second, Hz

Question 22

Frequency is determined by? Changed by sonographer? Typical values?

Answer 22

Sound source
No
2MHz -15 MHz

Question 23

What does frequency affect?

Answer 23

Penetration and axial resolution

Question 24

Formula for determining Hz?

Answer 24

Cycles/seconds

Question 25

Define ultrasound. Audible sound or inaudible sound?

Answer 25

Waves >20kHz | Inaudible

Question 26

Define infrasound. Audible or inaudible sound?

Answer 26

Sound with frequencies < 20Hz. | Inaudible

Question 27

What does reciprocal mean in regard to frequency and PERIOD?

Answer 27

Frequency x PERIOD = 1

Question 28

What three acoustic parameters describe a sound beam's strength?

Answer 28

Amplitude, power, intensity

Question 29

Amplitude is expressed in?

Answer 29

Decibels dB

Question 30

Amplitude is determined by? Changed by sonographer?

Answer 30

``` Sound source (initially) Yes - amplitude decreases as sound travels through the body ```

Question 31

The difference between maximum and minimum values of an acoustic variable is called what?

Answer 31

Peak-to-peak amplitude

Question 32

What is power's relationship to amplitude?

Answer 32

Power is proportional to (amplitude) squared

Question 33

What is the definition of intensity?

Answer 33

Concentration of energy in a sound beam Watts/cm2 Intensity = power (watts)/beam area (cm2)

Question 34

What does intensity depend on?

Answer 34

Power and the cross-sectional area of the beam

Question 35

What is the typical values for intensity?

Answer 35

0.001-100 watts/cm2

Question 36

Intensity is determined by what? Changed by sonographer?

Answer 36

``` Sound source (initially) Yes - intensity decreases as sound propagates through the body ```

Question 37

What is the relationship between power and intensity?

Answer 37

Intensity is proportional (directly related) to intensity

Question 38

What is the relationship between intensity and amplitude?

Answer 38

Intensity is proportional to the amplitude squared

Question 39

Wavelength is determined by what? Can it be changed by the sonographer?

Answer 39

Both the sound source and the medium | No

Question 40

Define wavelength.

Answer 40

Length or distance of single cycle. (Length of one boxcar)

Question 41

What does wavelength influence?

Answer 41

Axial resolution

Question 42

What is the typical value of wavelength?

Answer 42

0.1-0.8 mm (in soft tissue)

Question 43

What is the equation for wavelength in ANY MEDIUM?

Answer 43

Wavelength (mm) = prop. Speed (mm/us)/frequency (Hz)

Question 44

In soft tissue, sound with a frequency of 1 MHz has a wavelength of __________.

Answer 44

1.54 mm

Question 45

In soft tissue sound with a frequency of 2 MHz has a wavelength of ____________.

Answer 45

0.77 mm

Question 46

What is the rule in soft tissue for determining wavelength?

Answer 46

Divide 1.54 mm by frequency

Question 47

What is the equation for the wavelength in soft tissue?

Answer 47

Wavelength (mm) = 1.54mm/us/frequency (MHz)

Question 48

What are the units for propagation speed?

Answer 48

m/s | mm/us

Question 49

What is the propagation speed determined by?

Answer 49

MEDIUM ONLY -density and stiffness

Question 50

Can speed be changed by the sonographer?

Answer 50

No

Question 51

True or False? All sound travels at the same speed through any specific MEDIUM.

Answer 51

True - sound waves with frequencies of 5 MHz and 3 MHz travel at the same speed when traveling through the same MEDIUM

Question 52

What is SO IMPORTANT to remember about propagation speed?

Answer 52

ALL sound travels at the SAME SPEED in the SAME MEDIUM.

Question 53

Biological effects are also known as?

Answer 53

Bioeffects

Question 54

Higher frequency = __________ wavelength. (Shorter or longer)

Answer 54

Shorter

Question 55

Lower frequency = __________ wavelength. (Shorter or longer)

Answer 55

Longer