The conventional approach to achieving relatively uniform directional dispersion of sound from an audio monitor is to use diffraction from drivers substantially smaller than the wavelengths of sound they are reproducing. Ideally one would like to have a point sound source emitting a spherical wave front in at least a 90 degree cone. However, it is desirable to use larger drivers to counteract difficulties in producing sufficient amplitude and linearity. Larger drivers emit nearly planar wave fronts at higher frequencies that produce substantially larger amplitudes on axis, known as “beaming.” With the advent of 3D printing technologies, it is possible to print acoustic lenses that have negative focal length, better dispersing the sound. The approach uses an array of physical channels to delay portions of the planar wave front, shaping it into a spherical wave front having an apparent point source as illustrated by acoustic measurements and photography. In a practical speaker installation, the acoustic lens reduced the on-axis beaming effect by reshaping the driver’s planar wave front into a spherical one. Subjective impressions from listeners were very positive. 3D printing opens up the possibility of creating a range of such lenses for various purposes, particularly changing the shape and nature of emitted wave fronts.
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