EMF Glossary

A reference guide to electromagnetic field terminology used throughout our reviews and guides.

Measurement Terms

The reduction in signal strength, measured in decibels (dB). Higher dB means more blocking. 30dB = 99.9% reduction, 60dB = 99.9999% reduction.

A logarithmic unit measuring signal strength or attenuation. Every 10dB increase represents a 10x power reduction.

How often an electromagnetic wave oscillates per second, measured in Hertz (Hz). Cell signals use MHz (millions) and GHz (billions).

Electromagnetic waves in the 3kHz to 300GHz range. Includes cellular, WiFi, Bluetooth, GPS, and broadcast signals.

The invisible field produced by electrically charged objects. Includes electric fields, magnetic fields, and RF radiation.

Very low frequency fields (3-300Hz), typically from power lines and electrical wiring.

An enclosure made of conductive material that blocks electromagnetic fields. Named after scientist Michael Faraday.

A portable Faraday cage in bag form, typically made from metalized fabric or copper-nickel mesh.

How well a material blocks electromagnetic signals, measured in dB at specific frequencies.

Metal mesh fabric (copper, nickel, silver) that reflects and absorbs RF signals.

Connecting shielding material to earth ground to drain electric fields. Not always required for RF blocking.

Mobile phone signals. 4G uses 700MHz-2.6GHz, 5G uses 600MHz-39GHz.

Wireless networking signals at 2.4GHz and 5GHz bands.

Short-range wireless at 2.4GHz for device pairing.

Satellite positioning signals at 1.2GHz and 1.5GHz.

Near-Field Communication at 13.56MHz for contactless payments and access cards.

Radio-Frequency Identification, various frequencies for tracking tags and access cards.

A device that measures electric fields, magnetic fields, and RF simultaneously.

Advanced equipment that shows signal strength across a range of frequencies.

Measures magnetic field strength in Gauss or Tesla.

Last updated: January 2026