shielding: Many signals (see Signal), in the HiFi- and video systems are very small and weak. They are easily disturbed by external electric and magnetic fields. To prevent this, they are protected (shielded) by a shield. The cable is constructed like a kind of Faraday cage in which the signal can be transported largely protected. The effect (the degree of shielding) is measured in dB (see decibels) and describes the weakening of any interference.
When it comes to shielding a cable, there are major differences in the structure and, of course, in the effect. The simplest type is the so-called spiral shield. Here some wires are wound around the signal conductor(s) like a spiral. The effect is just sufficient. With a braided shield, wires are braided around the signal conductor in a very complex manner. The result is a larger area coverage and thus a better shielding effect. Another version is the foil screen. A mostly aluminum-coated Mylar foil is placed around the conductor(s). A bare drain wire establishes contact with ground.
Optimum shielding effects are achieved by combining different techniques. Double and triple shields combine spiral, braid and foil shields to improve performance.