Ch.9 Sound Beams

Question 1

What are the five terms that describe the shape and regions of a sound beam:

Answer 1

1. focus
2. near zone
3. focal length or near zone length
4. far zone
5. focal zone

Question 2

The ______________ is the location where the beam is the narrowest

Answer 2

The focal point is the location where the beam is the narrowest

Question 3

The focus is ________________ the width of the beam as it leaves the transducer

Answer 3

The focus is one-half the width of the beam as it leaves the transducer

Question 4

The _____________ zone is the region from the transducer to the focus, also known as ___________________, or _______________________.

Answer 4

The near zone is the region from the transducer to the focus, also known as near field, or fresnel zone

Question 5

The __________________ length is the distance from the transducer to the focus, also known as _____________________, or _________________________.

Answer 5

The focal length is the distance from the transducer to the focus, also known as focal depth, or near zone length

Question 6

The ___________ zone is the region that starts at the focus and extends deeper, and is also called the _______________, or _____________________________.

Answer 6

The far zone is the region that starts at the focus and extends deeper, and is also called the far field or Fraunhofer zone

Question 7

The __________________ zone is a region around the focus where the beam is relatively narrow

Answer 7

The Focal Zone is a region around the focus where the beam is relatively narrow

Question 8

At the transducer the beam diameter ________________ the transducer diameter

Answer 8

At the transducer the beam diameter equals the transducer

Question 9

At the focus the beam diameter is _________________ the transducer diameter

Answer 9

At the focus the beam diameter is one-half the transducer

Question 10

At 2 near zone lengths, the beam diameter _____________ the transducer diameter

Answer 10

At 2 near zone lengths, the beam diameter equals the transducer diameter

Question 11

Deeper than 2 near zone lengths, the beam diameter is _____________ than the transducer diameter

Answer 11

Deeper than 2 near zone lengths, the beam diameter is wider than the transducer diameter

Question 12

A beam with a larger diameter will have a ________________ focus

Answer 12

A beam with a larger diameter will have a deeper focus

Question 13

A beam with a smaller diameter will have a ___________________ focus

Answer 13

A beam with a smaller diameter will have a shallower focus

Question 14

Higher the frequency the _________________ focus

Answer 14

Higher the frequency the deeper the focus

Question 15

Lower the frequency the _____________________ focus

Answer 15

Lower the frequency the shallower the penetration

Question 16

Focal depth equation:

Answer 16

focal depth(mm)=diameter(mm)^2 x frequency (MHz)/6

Question 17

________________________________ describes the gradual spread of the ultrasound beam in the far field

Answer 17

beam divergence describes the gradual spread of the ultrasound beam in the far field

Question 18

smaller diameter beams ___________________ more in the fraunhofer zone

Answer 18

smaller diameter beams spread out or diverge more in the fraunhofer zone

Question 19

larger diameter beams _______________________ in the fraunhofer zone

Answer 19

larger diameter beams diverge less in the fraunhofer zone

Question 20

lower frequency causes _____________ divergence in the fraunhofer zone

Answer 20

lower frequency causes more divergence in the fraunhofer zone

Question 21

higher frequency causes ____________ divergence in the fraunhofer zone

Answer 21

higher frequency causes less divergence in the fraunhofer zone

Question 22

V-shaped wave is created when the source is about the size of the sounds wavelength. These V-shaped waves are also known as _______________________ waves, _______________________ patterns, or _____________________________wavelets

Answer 22

These V-shaped waves are also known as spherical waves, diffraction patterns, or Huygens wavelets

Question 23

_________________________________ states that a large active element may be thought of as millions of tiny, distinct sound sources.

Answer 23

Huygens’ Principle states that a large active element may be thought of as millions of tiny, distinct sound sources.