Recent observations of acoustic attenuation and velocity in superfluid 3HeB have revealed two order parameter collective modes of the BW-state. The dependence of the mode frequencies on temperature, pressure and magnetic field is reviewed. Identification of the modes from data is discussed, including possible corrections to weak-coupling predictions suggested by recent theoretical work. These modes can be conveniently viewed as Cooper-pair excited states classified according to total angular momentum. Measurements of the lifetime of these states is presented with a comparison to theory.
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