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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.

Author: Berstis, Viktors
Affiliation: IBM Corporation, Portland, OR, USA
JAES Volume 66 Issue 12 pp. 1082-1093; December 2018
Publication Date: December 20, 2018

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Author Response Viktors Berstis	Comment posted December 24, 2018 @ 16:39:39 UTC (Comment permalink) I have posted the STL files I used here:  https://www.thingiverse.com/thing:3309638 for those wanting to actually 3D print this.  - Viktors Berstis (Respond to this comment)
Tom Loredo	Comment posted January 5, 2019 @ 17:00:28 UTC (Comment permalink) Sorry to continue on this—looking at the HTML source, it appears the problem is that you included a non-breaking space in the URL (or the AES web interface added it). Take that out, and hopefully the URL will work. (Respond to this comment)
Author Response Viktors Berstis	Comment posted January 7, 2019 @ 20:15:07 UTC (Comment permalink) I was unable to prevent the break.  Perhaps the web site editors can fix this. Note from moderator: It has been fixed. (Respond to this comment)
Author Response Viktors Berstis	Comment posted February 3, 2019 @ 22:05:54 UTC (Comment permalink) Some have had trouble with spacing when copying the software from the pdf.  I have posted the source at http://berstis.com/lenspgm.sno for convenience in dealing with any such issues. This version includes code to emulate the science functions which might be missing from your version of SNOBOL4.  This code will run correctly unaltered using Minnesota SNOBOL4 available at the same site. (Respond to this comment)

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