Sound Beams

Question 0

What is the location where the beam reaches its minimum diameter?

Answer 0

The focus or focal point is the location where the beam reaches its minimum diameter.

Question 1

What types of beams create better images, narrow beams or wide beams?

Answer 1

Narrow beams create better images.

Question 2

What is the distance from the transducer face to the focus called?

Answer 2

Focal depth, focal length, or near zone length

Fresnel zone

Question 3

What is the name of the region or zone in between the transducer and the focus?

Answer 3

The near zone or Fresno zone is the region or zone in between the transducer and the focus. Sound beams converge in the near zone.

Question 4

What is the region or zone deeper than the focus, beyond the near field, where sound beams diverge?

Answer 4

The far zone or the Fraunhofer zone

Question 5

What is the region surrounding the focus where the beam is sort of narrow and the picture is relatively good?

Answer 5

The focal zone

Question 6

What is the beam diameter at the end of the near zone?

Answer 6

At the end of the near zone, the beam diameter is half the transducer diameter, or aperture.

Question 7

What is the beam diameter at two times the near zone length?

Answer 7

At 2 near zone lengths, the beam diameter is equal to the transducer diameter.

Question 8

At a distance greater than two near zones, is the beam diameter greater than, less than, or equal to the transducer aperture?

Answer 8

Since the beam diameter is equal to the aperture at two near zone lengths and it is diverging, then the beam diameter must be greater than the transducer aperture.

Question 9

What are the two determining factors of focal depth?

Answer 9

Focal death is determined by transducer diameter and frequency of the ultrasound beam.

Question 10

Would a beam with a small diameter and low-frequency have a shallow or deep focus?

Answer 10

Shallow focus

Question 11

Would a beam with a large diameter and a high-frequency have a shallow or deep focus?

Answer 11

Deep focus

Question 12

Sound beam divergence is determined by what?

Answer 12

The transducer diameter and the frequency of the ultrasound

Question 13

Would a larger aperture and high-frequency create more or less divergence in the far field?

Answer 13

Less divergence

Question 14

Would a small aperture and low-frequency create more or less divergence in the far field?

Answer 14

More divergence and degraded lateral resolution

Question 15

What’s another name for a V-shaped wave?

Answer 15

Huygen’s wavelet

Question 16

This principle explains the hourglass shape of an imaging transducers sound beam:

Answer 16

Huygens’ principal

Question 17

What determines the frequency of sound created by a pulsed-wave transducer?

Answer 17

Thickness of ceramic and speed of sound

Question 18

The ability to distinguish two structures that are close to each other front to back, parallel to, or along the beams main axis.

Answer 18

Axial resolution

Question 19

What does LARRD Resoultion stand for?

Answer 19

Longitudinal, axial, range, radial, depth

Question 20

Do shorter or longer pulses provide better axial resolution?

Answer 20

Shorter pulses