On each map the Umklapp sample and relative source location are indicated the maps plotted above and below the plate are the simulated (on the left of the plate normal) and measured (on the right of the plate normal) absolute pressure fields. Panels (a)–(f) display composite maps of the absolute pressure field ( | p |) comparing numerical simulations and measurements. The small sources of sound producing these wavelets are known as Huygens' sources Huygens' Principle: tiny pieces of PZT create V-shaped waves that interfere constructively (to form hourglass shape) and destructively (sound beam is cancelled) to create an hourglass-shaped beam.(Top left),(top right) Numerical model band-diagram analysis displaying the allowed scattering processes and resulting beaming angles for our experimental sample, for point-source acoustic excitation on the unstructured (top left) and structured (top right) when the pressure field is evaluated on the opposite side of the plate.AKA diffraction patterns, or Huygens' wavelets.V-shaped wave is created when the source is about the size of the sound' s wavelength.Definition is imprecise 1 Shallow Focus Deep Focus Smaller diameter PZT Larger diameter PZT Lower frequency Higher frequency Spherical Waves: sound waves produced by very small sources (tiny pieces of PZT) diverge in the shape of a 'V'.Half the focal zone is located in the near zone, and half in the far field.Region around the focus where the beam is relatively narrow.At the beginning of the far zone, beam is only ½ as wide as it is at the transducer at 2 near zone lengths it is same size as transducer at more than 2 near zone lengths it is larger than the diameter of the transducer 5.Region that starts at the focus and extends deeper.Fixed focus transducer- depth is determined by: ○ Transducer diameter ○ Frequency of the sound 4.Phased array- modern, adjustable focus systems.Distance from the transducer to the focus.(Focus is located at end of near zone) 3. Width as it leaves the transducer is the same as the diameter of the active element, it narrows to ½ at the focus.Width is ½ the width of the beam as it leaves the transducer 2.AKA 'focal point', 'end of near zone', 'beginning of far zone', 'middle of focal zone'.2 More divergence Less divergence Smaller diameter Larger diameter Lower frequency Higher frequencyĬhapter 9: Sound Beams Anatomy of a Sound Beam: 1. The small sources of sound producing these wavelets are known as Huygens' sources Huygens' Principle: tiny pieces of PZT create V-shaped waves that interfere constructively (to form hourglass shape) and destructively (sound beam is cancelled) to create an hourglass-shaped beam. Chapter 9: Sound Beams Anatomy of a Sound Beam: 1.
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