CBR (Center Bout Romboid, also called C2), normally 380 .. 420 Hz
CBR has mainly symmetrical twisting motion of the corpus with the C bout areas moving in opposite phase, and is the easiest of all modes to recognize. While quite active, it is usually not a strong radiator of sound, due to phase cancellation from the symmetrical vibration pattern—one side is pumping air out while another side sucks air in. CBR is a also a special case in that the mode shape still exists without a soundpost or with the soundpost set at the centre join. It.
See more CBR animations on the next page.