RPG BAD Arc
BAD™ Arc is the acoustic industry’s first digital, curved, sound diffuser. It consists of absorptive and reflective areas optimally positioned according to a 2-dimensional binary sequence, where “zero” represents absorption and “one” represents reflection. The resulting binary amplitude grating offers diffusion above 1 kHz and transitions to absorption below. The curve featured by the BAD™ Arc further increases the ‘specular’ (or first reflection) performance of the binary amplitude grating, expanding both the diffusion and absorption capabilities. Thus, the BAD™ Arc offers a high performance hybrid surface with the aesthetic of a traditional fabric wrapped panel.
The original ‘flat’ BAD™ panel was the first panel to utilize a variable impedance surface using a unipolar optimal binary sequence of holes. It provides omnidirectional diffusion working as an amplitude grating. Having approximately 50% open area, it can reduce the specular scattering by 6 dB. To improve upon this, the BAD™ Arc utilizes a curved configuration of the grating which causes all of the reflective areas to no longer be in phase with each other and thus improves the polar response. This, in turn, improves the diffusion coefficient.
In the graph below, you can see the appreciable diffusion gain (in dB) which results from curving the panel. Keep in mind 1dB is just noticeable, 3 dB is clearly noticeable, 6 dB is very noticeable and 10 dB offers a two fold improvement in performance.
The graph illustrates how the BAD™ Arc offers broad bandwidth absorption below 1000 Hz, and a decreased absorption above this frequency where the panel is transforming into a sound diffuser. The binary template allows the sound above 1000 Hz, which was conventionally lost to absorption, to be uniformly diffused providing reflection control without destroying the room’s ambience.
The Digital Story
To accomplish diffsorption, RPG® researchers developed a planar 2 dimensional binary reflection amplitude grating consisting of a 31 x 33 element array of 1,023 0.5 sq. in. absorptive or reflective areas. The reflective areas map to the “1” bit and the absorptive areas map to 0, or vice versa. The distribution of these ‘resorptive’ binary elements is based on a 2 dimensional optimal binary sequence with a flat power spectrum. The resulting variable impedance surface forms a binary reflection amplitude grating as suggested originally by James Angus. This is in contrast to RPG®’s reflection phase gratings which use phase variation, rather than amplitude variation, to provide diffusion.
The Binary Amplitude Diffsorbor™ (BAD™) grating provides diffusion about an octave above the frequency whose wavelength is twice the size of the binary element. This explains the limitation of traditional variable impedance arrays. For example, 1′ x 1′ panels provide diffusion up to about 1 kHz. Remaining high frequency reflections would still corrupt speech and music quality.
Installation of the BAD™ Arc is quick and easy. Simply use impaling clips to mount to wall, or choose one of our mounting options. Cloud anchors are available for suspending overhead.