Measurement of acoustic fields using schlieren and holographic techniques

Abstract

Two methods, schlieren imaging and acoustical holography, are shown to be useful for quantitatively measuring detailed nearfield and farfield acoustic radiation patterns from a submerged cylindrical target. The two imaging methods are discussed so as to illustrate the fundamental mechanisms of imaging involved. The advantages and limitations of each are made clear, and examples of typical laboratory acoustic field measurements are shown for a cylindrical aluminum target. The farfield of the target is computed from an emerging theory for nonrigid cylinders, and the experimental farfield data obtained holographically is shown to agree with that theory. The nearfield of the same target is plotted directly from the photo intensity of the schlieren image.