TB - Transducer (Chp 2)

Question 1

How does thickness of the tx/crystal relate to frequency?

Answer 1

thicker beam produces a lower freq

Question 2

What is the formula for the frequency of the TX for pulsed-wave operation?

Answer 2

Operating Freq = c/ (thickness X 2)

Question 3

The operating frequency is also about 1/2 of what?

Answer 3

the wavelength

Question 4

Define depth ambiguity?

Answer 4

This is an artifact that occurs when the tx. sends out a pulse before the previous one has returned. and it therefore cant figure out where it originated to display it correctly

Question 5

What is Huygens Princuple

Answer 5

The sound beam starts out as small wavelets at tx face –> these form a sounds beam while traveling perpendicular to the wave front

Question 6

What does the housing of the transducer do?

Answer 6

provides insulation and protection from electrical shock

Question 7

What are the advantages of the damping/backing materal?

Answer 7

decreases number of cycles in a pulse (ringing period), decreases SPL, increases axial res

Question 8

What is the backing material made of?

Answer 8

epoxy resin and tungsten

Question 9

What are the side effects/disadvantages of dampening?

Answer 9

• decreases sensitivity and increases BW

- reduces QF

Question 10

What is the Quality Factor?

Answer 10

term to quantify the purity of the beam

operating freq/bandwidth

Question 11

What is the process of phasing to steer?

Answer 11

Changing the timing of shocking the elements in order to shape/steer the beam

Question 12

What else is the technique of phasing used for?

Answer 12

focusing by firing the peripheral elements first

Question 13

What is a CW transducer?

Answer 13

1 element to continuously transmit sound and one that continuously receives sound - produces no image

Question 14

How can we decrease the SPL?

Answer 14

• decreasing wavelength by increasing the frequency

- decreasing the number of pulses per SL by increasing damping material

Question 15

Do we want a high number of axial resolution or low?

Answer 15

the lower the number = the closer the objects can be - which is what we want

Question 16

What is the SPL formula?

Answer 16

SPL = wavelength x n

Question 17

What is the wavelength formula?

Answer 17

c/f

Question 18

What type of resolution is usually better in transducers, axial or lateral?

Answer 18

axial resolution

Question 19

What can a 1.5D array tx do that a 1D cant?

Answer 19

it can focus the beam in the elevational plane

Question 20

What minimun FR needs to be obtained or else the image will flicjer?

Answer 20

atleast a FR of 15 Hz

Question 21

What is the FR formula?

Answer 21

FR = PRF/LPF (lines per frame)

Question 22

What is dropout

Answer 22

occurs on an image as. a black line when tx is damaged

Question 23

Which is the type of transducer that utilizes elements arranged in a concentric pattern?

Answer 23

Annular Array

Question 24

Which transducer has moving parts?

Answer 24

mechanical array

Question 25

What happens to the diameter of the sound beam in the fresnel zone?

Answer 25

it decreases

Question 26

How can you increase the NZL?

Answer 26

increase the aperture and the frequency

Question 27

What will decrease beam divergence in the far field?

Answer 27

Increase the aperture and frequency

Question 28

What is angular resolution another name for?

Answer 28

lateral resolution

Question 29

What happens to the frequnecy with a thin crystal element?

Answer 29

it will give a higher frequency