# Ch 9: Sound Beams Flashcards

1
Q

This is the location where the beam is the narrowest.

A

focus or focal point

2
Q

The width of the sound beam at the focus is ___ the width of the beam as it leaves the transducer.

A

one half

3
Q

This is the region from the transducer to the focus.

A

near zone, near field, Fresnel zone

4
Q

This is the distance from the transducer to the focus.

A

focal depth, near zone length

5
Q

This is the region that starts at the focus and extends deeper.

A

far field, Fraunhofer zone

6
Q

When the beam is two near zone lengths from the transducer, the beam is ___ as the active element.

A

the same size

7
Q

At depths more than two near zone lengths, te beam is ___ than the active element.

A

wider

8
Q

This is a region around the focus where the beam is relatively narrow.

A

focal zone

9
Q

A

phased array.

10
Q

What characteristics of a fixed focus transducer determine the focal depth?

A
• transducer diameter

- frequency of sound

11
Q

How does transducer diameter affect the focal depth?

A

The larger the diameter, the deeper the focus.

12
Q

Transducer diameter and focal depth are ___ related.

A

directly

13
Q

How does frequency affect focal depth?

A

The higher the frequency, the deeper the focus.

14
Q

Frequency and focal depth are ___ related.

A

directly

15
Q

This describe the gradual spread of the u/s beam in the far field.

A

beam divergence

16
Q

What characteristics of a transducer determine the spread of the beam in the far field?

A
• transducer diameter

- frequency of the sound

17
Q

How does transducer diameter affect beam divergence in the far field?

A

The smaller the diameter, the larger the spread of the far field.

18
Q

Crystal diameter and beam divergence are ___ related.

A

inversely

19
Q

___ diameter crystals improve lateral resolution in the far field.

A

Larger

20
Q

How does frequency alter beam divergence in the far field?

A

The lower the frequency, the larger the spread of the far field.

21
Q

Frequency and beam divergence are ___ related.

A

inversely

22
Q

___ frequency sound improves lateral resolution in the far field.

A

Higher

23
Q

Sound waves produced by small sources diverge in the shape of a ‘V’ called…

A

Huygens’ wavelets, spherical waves, diffraction paterns

24
Q

The small sources of sound producing Huygens’ wavelets are known as…

A

Huygens’ sources.

25
Q

___ describes why ‘V’ shaped wavelets form an hourglass-shaped beam.

A

Huygens’ Principle