Shielding effectiveness refers to the ability of a material or structure to block or reduce electromagnetic interference (EMI) from external sources. This is crucial in various applications, such as electronics and telecommunications, where unwanted signals can disrupt performance. The effectiveness is often measured in decibels (dB), indicating how much the material can attenuate the incoming electromagnetic waves. Factors influencing shielding effectiveness include the material's conductivity, thickness, and frequency of the EMI. Common materials used for shielding include metals like copper and aluminum, which are known for their high conductivity. Proper design and installation are also essential to maximize the shielding performance in devices and systems.