Cell phones became popular in the U.S. in the 1990s. They continue to evolve as we assess how they interface with the human body, the environment and other technology. Both natural and man-made materials affect cell transmissions. Cell signals can be totally or partially blocked and absorbed by materials that conduct electricity. Whenever electromagnetic energy, which powers a cell phone, comes in contact with a conductor, there is a reaction. Recent studies have pinpointed certain materials that have the most impact on cell signals.
Conductive and Non-Conductive Material
Science students at California State University tested their hypothesis that conductive material is more likely to block cell-phone transmissions than non-conductive material. They studied how different materials affected cell-phone transmissions by placing a cell phone inside a variety of enclosures containing tin foil, plastic, wood, salt water and tap water. They called the cell phone and evaluated the strength of the signal in relation to these materials. They presented the results at the 2007 California State Science Fair, noting that conductive materials, such as tin foil and salt water, completely blocked the cell signal. Water, another conductor, weakened the signal, while wood and plastic, which are non-conductors, did not affect the signal.
Construction materials used in the home or office may affect your cell signal. Cell signals do not have strong penetration through metal, aluminum and concrete. Some high-security buildings are constructed with a wire mesh known as a "Faraday cage." This is a metallic enclosure made from fine-mesh copper screening. It creates a conductive shell that prevents the entry or escape of any electromagnetic field. Faraday cages are used in electronic labs to prevent electromagnetics from interfering with electronic testing. They are also used as a security precaution to prevent hackers from remotely viewing classified or proprietary on-screen computer data. A building with this copper wire mesh encasement prohibits cell phones from sending or receiving any signals.
Salt water prohibits radio waves from traveling because salt contains ions, and water is a conductor. Plants, mountains and hills also affect cell signals. Plants contain water and dissolved ions, which conduct electricity. Mountains and hills often act as obstructing materials, breaking the contact between your cell phone and a cell tower, which results in a weaker signal.
Radio Frequency Interference
Radio frequency interference is a disturbance that interrupts, obstructs, or limits the effective performance of a circuit. According to SignIndustry.com, radio frequency interference (RFI) refers to any "unwanted" signal received by a device that prevents clear or best "wanted" signal reception. RFI can affect any signal-receiving system, such as televisions, computers and cell phones. Any device that generates or uses radio frequency can cause radio frequency interference. Also, according to SignIndustry.com, communication equipment in your home, microwave ovens, street lamps, aquariums, lighting systems and other electrical devices and equipment can all affect cell signals.