BAD PANEL CONTINUED

Figure 1. BAD™ panel sample showing a partial binary amplitude grating template (top) and optional fabric covering (bottom) with a beveled edge detail

In DRV6I2 and DRV6I3 we introduced and described several characteristics of the BAD™ panel. This novel, flat, diffsorptive surface has found widespread use in almost every architectural acoustic application and is currently being aggressively specified.

Figure 2. Comparison of the absorption coefficient for a 1” fiberglass panel and a BAD™ panel with 5/8” and 1/2” holes. Note the decrease in absorption above 1 kHz for the 1/2” holes. This energy, formerly removed, can now be diffused adding ambiance along with reflection control

The BAD™ panel offers reflection control above 1000 Hz, by diffusing the sound, rather than absorbing it. Below 1000 Hz, the BAD™ panel offers pure absorption, with improved efficiency compared to a standard fabric wrapped panel. There have been requests from the acoustical community to further attenuate the absorption above 1 kHz to offer additional ambiance and diffusion. In Figure 2, we compare the absorption of a 1” traditional fabric wrapped panel, a 1” BAD™ panel with 5/8” holes and one with 1/2” holes. Note the additional attenuation above 1 kHz for the 1/2” holes. RPG’s new reverberation chamber and impedance tube measurement facilities give us the opportunity to perform constant engineering evaluations and what-ifs upon the request of the acoustical community. In Figure 3, we present random incidence absorption coefficients for the BAD™ panel in thicknesses of 1”, 2”, 3” and 4” compared to a traditional 1” fabric wrapped panel. Note that additional thicknesses of fiberglass increase the low frequency absorption, while maintaining the attenuation above 1 kHz. These data emphasize the power of the BAD™ panel to provide absorption as needed below 1 kHz, while simultaneously minimizing absorption above 1 kHz to allow the room to have ambiance.

Figure 3. Comparison of the BAD™ panel’s sound absorption for thicknesses of 1”, 2”, 3” and 4” with 1/2” holes.

In DRV6I2 and DRV6I3, available online at www.rpginc.com/news/reflections.htm, we have presented the diffusion coefficient for the BAD™ panel for normal and glancing incidence. In Figure 4 of this Issue, we present new balloon plots illustrating how the BAD™ panel scatters more uniformly than a flat panel of comparable size above 1 kHz, for normal incidence.

4a Flat 1 kHz

4b BAD 1 kHz

4c Flat 2.8 kHz

4d BAD 2.8 kHz

Figure 4. Comparison between 3D balloon plot for a flat reflective surface and the BAD™ panel at normal incidence. (4a) Flat panel at 1000 Hz, (4b)BAD™ panel at 1000 Hz, (4c) Flat panel at 2800 Hz, (4d) BAD™ panel at 2800 Hz. Note improved diffusion uniformity in 4b and 4d compared to 4a and 4c