Electrophysiology: how to get rid of noise in paired recordings?

[nabila_haji]

I have a question about the noise during paired recordings. when I connect two headages to the same reference or to two separate references, the noise is higher. When I unplug one reference, the noise disappears. It seems like the two references are sharing the noise.
I adjusted the angle of the manipulators, and connected the reference to the earth ground or signal ground, but it doesn’t help to decrease the nois.
Please if you have any suggestions. Thanks alot in advance.