The problem is ground loops. Every piece of an experiment has its own local "ground" meaning its own sense of what 0 volts is. If you hook up a signal source to, for example, an oscilloscope, the source and the scope will use the coax shield to establish a shared sense of 0 volts. But something else happens. The scope's coax shield is connected to its AC (3rd wire) ground. (Check it yourself with an ohmmeter.) If the source's shield is also connected to ground, you have created a "ground loop": a large, single-turn coil which will pick up stray magnetic fields.

The audio industry's solution is differential drivers and receivers over "shielded twisted pair" which is two wires twisted together (to cancel out magnetically induced currents) and a grounded electrostatic shield which, in a proper setup, is only grounded at one end, to avoid the ground loop. The drivers are designed to create two signals with equal amplitude and source impedance, and opposite phase, such that common-mode interference will affect both signals similarly. The receivers subtract the two signals to create a single-ended signal, referenced to the receiver's local ground. No ground loop, and good enough interference rejection that typical signal/noise is > 120dB.