Week 2 Assessment (6,7,8)

Question 1

logarithms

Answer 1

Count the zeros.Ex.log of 100 is 2.

Question 2

Positive decibels and negative decibels

Answer 2

Positive:Intensity doubles for every 3bD
Ex. 9dB (two 3s to get 9 so 2 x 2= 4 times larger)
Negative: -3dB:1/2 ..example—6dB=1/2x1/2=1/4
-10dB: 1/10…ex.9dB=1/2x1/2x1/2=1/8

Question 3

Attenuation is directly related to

Answer 3

Distance and frequency
longer distances, higher frequencies= more attenuation

Question 4

3 components of attenuation

Answer 4

Absorption, scattering and reflection

Question 5

Media with least attenuation

Answer 5

water

Question 6

Media with most attenuation

Answer 6

Air

Question 7

what’s the conversion of acoustic energy into heat?

Answer 7

Absorption

Question 8

Primary cause of attenuation in soft tissue (80%)

Answer 8

Absorption

Question 9

Absorption is_________related to distance and frequency

Answer 9

directly

Question 10

Sound that returns back to the transducer after striking a boundary

Answer 10

Reflection

Question 11

The 2 forms of reflection are

Answer 11

Specular:
(smooth reflector, one direction, smaller wavelength than boundary irregularities)
Diffuse/backscatter:
(rough reflector, random directions, wavelength same size as boundary irregularities)

Question 12

Boundary’s irregularities are same size to bit smaller than wavelength, wave redirected in all directions.High frequencies have more …ex.Red blood cells are this

Answer 12

Rayleigh scattering

Question 13

Thin half value layer

Answer 13

Bone
high freq,high attenuation rate

Question 14

thick half value layer

Answer 14

Fluids
low freq,low attenuation rate

Question 15

what other names half value layer known by

Answer 15

penetration, depth of penetration, half boundary layer

Question 16

sound beam strikes boundary exactly at 90 degrees

Answer 16

Normal incidence

Question 17

Any angle other than 90 degrees is

Answer 17

Oblique incidence
acute<90
Obtuse >90

Question 18

Formula for incident intensity

Answer 18

Reflected intensity + Transmitted intensity

Question 19

% reflected for soft tissue,bone and air

Answer 19

soft tissue: less than 1%
Bone : 50%
Air : 99%

Question 20

Formula for IRC(%)–reflection with normal incidence

Answer 20

(Z2-Z1/Z2+Z1)^2
Z1= reflection #
Z2= Transmission #

Question 21

Reflection with normal incidence (90 degrees) occurs when (IRC)

Answer 21

there are different impedances on either side of the boundary

Question 22

Transmission with normal incidence occurs (ITC)

Answer 22

When the Two media have same impedance
% from reflected sound - 100%= ITC

Question 23

Transmission with oblique transmission

Answer 23

100% IRC +ITC
transmission difficult to predict

Question 24

Refraction cannot occur with

Answer 24

Normal incidence or with identical propagation speeds.

Question 25

Refraction is and requires

Answer 25

when the direction of wave propagation is changed from 1 medium to another
requires :
Oblique incidence and diff propagation speeds of 2 media

Question 26

Snell’s slaw is the reason

Answer 26

-Refraction occurs.
-Greater the change in the speeds of the media the greater the change in the angle of refraction
sin(transmission angle)/sin (incident angle)=propagation speed 2/propagation speed 1

Question 27

medium 1 and medium 2 refraction (oblique angle)

Answer 27

If md 1 is > md 2 travel in same direction
md 1 < md 2 ,md 2 is faster,shorter
md 1 > md 2 ,md 2 is slower, longer

Question 28

Thickness of matching layer

Answer 28

1/4

Question 29

thickness of active element (pzt)

Answer 29

1/2

Question 30

3 consequences of using backing material

Answer 30

decreased sensitivity
wide bandwidth
low quality factor

Question 31

Resonant frequency

Answer 31

ringing at single frequency

Question 32

Main frequency of transducer known as

Answer 32

center, resonant,primary or natural frequency

Question 33

Quality factor

Answer 33

Main frequency/ bandwidth
ex.7hz/8hz-6

Question 34

transducer that has Low Q due to backing material

Answer 34

Imaging transducers

Question 35

therapeutic imagining has

Answer 35

HIGH Q

Question 36

Speed of sound in PZT and frequency are

Answer 36

directly related

Question 37

Thickness in PZT and frequency are

Answer 37

inversely related