Brown noise is sound whose upper frequency components drop off at a rate of 6dB/octave, as distinct from pink noise which has a 3dB/octave drop, and white noise which has a uniform amplitude at all frequencies. From a practical standpoint, pink noise is probably the most useful for purposes of testing audio equipment.
Ground noise is ambient noise which is detected even when the input to a device is shorted and should be completely quiet. It represents the baseline noise level of a system.
Ground noise would seem more apropos here from a technical standpoint, but 'brown noise' could appeal on the basis of scatological or historical references.
See #13. I think this explains it.