with a deep airspace filled with supplemental absorptive material. In this configuration, very low frequencies are absorbed making an effective bass trap. absorption behind the panel. NRC range 0.70 - 0.90. Grilles -- wood slats, horizontal or vertical, with space between them. Absorption occurs by placing supplemental absorptive material either above or behind the slats. Since they have a high open area that exposes the absorptive materials to the soundwaves, absorption is relatively broadband. The acoustic performance varies based on the dimensions of the slats, the spacing between the slats and the supplemental absorption used. NRC range 0.70 - 0.95. Another interesting use of this material is to use small gaps between horizontal slats Wood Wool -- a material that's been available for many years. Manufactured in panels and constructed from cement bound Spruce wood wool. The absorption characteristics are fairly low NRC (0.4), however when placed over supplemental absorptive material it becomes a very effective, durable broadband absorber. NRC range 0.40 without supplemental absorption through 0.9 installed with 1" fiberglass board (See below). spring 2020 I designsolutions 51