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In [1] is shown that very close (distance smaller than L/2Π) to a vibrating and flat structure with typical size L, the normal particle velocity and the (normal) structural velocity coincide. It is shown that with an acoustic particle velocity sensor the normal acoustic particle velocity close to the surface can be measured and that this velocity coincides with the surface velocity that is measured with a laser vibrometer or accelerometer. In [1] it is also shown that in the very near field (contrary to the behavior in the near field) the particle velocity level doesn't depend upon frequency. Furthermore, in the very near field, there is a linear relationship between the particle velocity as measured and the structural velocity to be measured.

Spot defect repair systems for automotive paint finishes have enjoyed a great deal of success in domestic and foreign automotive markets over the past ten years, saving both time and money by eliminating the need for scrapping or refinishing defective parts. These systems typically involve sanding with a fine grade coated abrasive to remove the defect followed by compounding to remove sanding scratches. While compounding has been shown to work extremely well on rigid enamel base coat/clear coat finishes, it becomes less effective on newer, flexible two-component polyurethane (2K PUR) coatings. These low glass transition temperature materials exhibit elastic behavior under ambient conditions and are resistant to compounding using conventional methods. However, it has been found that compounding is effective on these materials if they are cooled below their glass transition temperatures. This process is known as cryogenic finishing.