Twisting the two wires of a pair causes each wire to be, on average, the same distance from any external noise source over the length of the cable. Any electromagnetic interference (EMI) or crosstalk from a nearby wire pair therefore induces nearly equal noise voltage on both wires.

Since the receiver measures the difference in voltage between the two wires (differential signaling), noise that affects both wires equally gets cancelled out. The tighter the twist (more twists per unit length), the better the noise cancellation — this is why Cat 5e/Cat 6 cables have progressively tighter twist rates than older cabling.