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SPI Review 11
Sound Beams
| Narrow beams create ___________images | better |
| As sound travels, the __________ of the beam changes | width |
| A sound beam starts out at exactly the same size as the ______________ or ___________, Then the beam gets progressively ___________until it reaches its smallest diameter, and finally the beam __________. | Transducer diameter or aperture, narrower, diverges |
| The location where the beam reaches its minimum diameter is call the? | Focus, focal point |
| The distance from the transducer to the focus. Can also be called what? | Focal depth, focal length or near zone length |
| The region or zone in between the transducer and the focus. It is also called what? | Near zone, Fresnel Zone |
| Sound beam __________ in the near zone. | Converge |
| The region or zone deeper than the focus, beyond the near field. It is also called what? | Far Zone/Fraunhofer Zone |
| Sound beams ___________ in the far zone. | Diverge |
| The region surrounding the focus where the beam is “sort of narrow” and the picture is relatively good is the _____________ | Focal zone |
| The beam diameter for an unfocused CW disk transducer at the level of the transducer is what size? | ½ the transducer aperture |
| The beam diameter for an unfocused CW disk transducer at the end of the near zone is what size? | Same as transducer aperture |
| The beam diameter for an unfocused CW disk transducer at 2 near zone lengths is what size? | Greater than transducer aperture |
| Focal Depth is the distance from the __________ to the _________ | Transducer, focal point |
| The focal depth is determined by what two factors? | Transducer diameter/aperture and frequency of ultrasound |
| A beam that has a shallow focus has a __________ diameter and a ________frequency | Small, low |
| A beam that has a deep focus has a ___________diameter and a _________ frequency. | Large, higher |
| Beams with a deep focus have a ______________ intensity at the focus when compared to beams with a shallow focus. | Lower |
| What describes the spread of the sound beam in the deep zone? | Sound beam divergence |
| Sounds beams with a larger aperture or larger diameter active element have __________ divergence. | less |
| Sound beams with less divergence have _____________ frequency | high |
| Sound beams that have less divergence have a ___________ beam in the far field. | narrower |
| Sounds beams with less divergence have _________ lateral resolution in the far field. | improved |
| Larger Diameter crystals produce _________frequency sound, and produce beams that diverge ________ in the far field | higher, less |
| Smaller aperture or smaller diameter active elements produce beams with _________ divergence | more |
| Sound beams with more divergence have a ___________ frequency | low |
| Sound beams that have more divergence have a _________ beam in the far field. | Wider |
| Sound beams with more divergence has ____________ lateral resolution in the far field. | Degraded |
| Smaller diameter crystals produce __________ frequency sound, and produce beams that diverge ____________ in the far field. | Low, substantially |
| Frequency of a CW sound beam is determined by what? | Electronic frequency |
| Frequency of a pulsed sound beam is determined by what? | Thickness of ceramic and speed of sound in ceramic |
| The focal length of a sound beam is determined by what? | Aperture of the active element and frequency of sound |
| Divergence of the sound beam is determined by what? | Aperture of the active element and frequency of sound |
| What is produced by a tiny source with a size near the wavelength of the sound, causing the ways to diverge into a v shaped wave? | Diffraction pattern |
| What is another name for the V-shaped wave seen in the diffraction pattern? | Huygens’ wavelet |
| What is the principle that explains the hourglass shape of an imaging transducer’s sound beam? | Huygens’ Principle |
| Each tiny part of the surface of the large transducer face may be considered an individual tiny sound source, creating _____________ | Huygens’ wavelet |
| The overall hourglass shape of sound beam is the result of the ________________________ of the many sound wavelets emitted from these numerous sound sources. | Constructive and destructive |
| When all of Huygens’ wavelets are combined, what is formed? | Hour glass shaped sound beam |
Created by:
dawncoffield