Lecture 13

Question 1

Piezo composites are added to decrease _____, and increase _____, _____ and _____

Answer 1

Decrease impedance

Increase bandwidth, sensitivity and resolution

Question 2

Damping material aka

Answer 2

Backing material

Question 3

Damping material is on ________ of element

Answer 3

Back

Question 4

Damping material has similar impedance to

Answer 4

Crystal

Question 5

Damping material is made of

Answer 5

Metal powder and plastic/epoxy resin

Question 6

Damping material reduces _______

Answer 6

Ringing and

cycles per pulse (n) ‘faster decay time’

Question 7

Decreased PD and SPL by damping material =

Answer 7

Better resolution and increase band width

Question 8

Damping material weaker sound going out =

Answer 8

Weaker echo coming in

Question 9

Damping material decreases ____ which is the abilitiy to _______

Answer 9

Sensitivity

Ability to detect echoes

Question 10

CW has no ____ thus has better ______ and worse ______

Answer 10

Damping material

Better sensitivity

Worse resolution

Question 11

Housing unit/case usually same material as

Answer 11

Damping material

Question 12

Housing unit/case prevents

Answer 12

Moisture and protects some of the internal structures

Question 13

Housing unit/case mainly absorbs

Answer 13

Energy from sides of crystals

Question 14

Impedance of transducer is ________ x the tissue

Answer 14

20x

Question 15

IRC of the matching layer is about ___ %

Answer 15

80%

Question 16

In the matchign layer, ______ layers are used to reduce __________

Answer 16

1-3 layers

Reduce the large differences in impedances

Question 17

We want

Answer 17

More transmission, less reflection

Question 18

Order of transmission through transducer

Answer 18

Element 
Matching layer 1
Matching layer 2 
Gel
Soft tissue