Nearfield acoustic hologr.aphy is used to reconstruct the velocity distribufion of an acoustic source located in a cylindrical space. Two reconstruction algorithms have been developed, both of which account for the boundary effects of the cylindrical walls. The first algorithm models the space as an infinite duct, while the second models the space as a finite duct. A known source velocity distribution is used to simulate a pressure field in the space. Pressures on the holography surface are processed by the holography algorithms to reconstruct the source velocity distribution. The results of the algorithms are compared, with particular attention to the sensitivity of reconstructions to the location, number, and spacing of sensors, aperture lengths, and measurement noise. tacting instrumentation. A system composed of a scanning laser vibrometer with computer-controlled optical scanner allows for noncontacting measurement of the amplitude and phase of the vibration velocity of a structural member. The laser vibrometer has a dynam!c range of 160 dB and broadband frequency response of up to 25 kHz. The vibrometer is held steady on a seismically isolated optical table and a mirror is positioned accurately by a computer-controlled stepper motor. The measurement of nearfield or farfield structural intensity at a point requires the measurement of the structural velocity at a minimum of four points for a beam and eight points for a plate about that point. Thus the amplitude and phase of the velocity field on the surface of a structure is measured at a fine mesh of discrete number of points. Error analysis is performed to assess the theoretical error introduced by the mesh size, number of points used for evaluating the structural intensity, random phase and amplitude errors, and errors introduced by nonsimultaneous measurements. 8:55 JJJ3. Measurement of flexural and longitudinal vibration intensity by a two-channel laser vibrometer. Timothy E. McDevitt, Courtney B. Burroughs (Appl. Res. Lab., Penn State Univ., State College, PA 16804), and Gary H. Koopman (Mech. Eng., Penn State Univ., State College, PA 16804)
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.