The question is quite self-explanatory. What word can be used to describe something that blocks radio waves?

Edit: No, I am not looking for some easy word like "block" or "blocker". This is part of a project, and I need a word that sounds sophisticated.

Edit 2: Sentence example:

_______ has a high attenuation coefficient.

I went to this website looking for an answer. I didn't find one... However, it explains what radio waves are pretty well, though.



  • Maybe electromagnetic interference. You'll have to read the technical definition to see if this is what you had in mind. See also radio jamming. – vpn Feb 27 '17 at 18:11
  • Can you provide an example sentence of how the word will be used? Also, what research have you performed on your own before posting here? – Hank Feb 27 '17 at 18:49
  • @Hank you should see it now. – Emereal Feb 27 '17 at 19:07
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    Do not confuse jamming with shielding. The first is "active", and the second is "passive". – Cascabel Feb 27 '17 at 20:40
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    How about "The substance is opaque to electro-magnetic radiation at radio frequencies."? – peterG Feb 28 '17 at 0:48

The material is called shielding. A small device is a shield. Bigger devices designed to isolate a large volume are called Faraday cages.

A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed such that they cancel the field's effect in the cage's interior. This phenomenon is used to protect sensitive electronic equipment from external radio frequency interference (RFI). Faraday cages are also used to enclose devices that produce RFI, such as radio transmitters, to prevent their radio waves from interfering with other nearby equipment. They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes through the interior.


If you are trying to block RF from being transmitted by a wire, that is an RF filter. The little lumps on your phone charger are called ferrites.

A ferrite bead or ferrite choke is a passive electric component that suppresses high frequency noise in electronic circuits. It is a specific type of electronic choke. Ferrite beads employ high frequency current dissipation in a ferrite ceramic to build high frequency noise suppression devices. Ferrite beads may also be called blocks, cores, rings, EMI filters, or chokes.


  • Also "RF shielding". – Keith McClary Feb 27 '17 at 22:47
  • No. "What do you call something that blocks radio waves?" "A Faraday cage" is like "What do you call a thing made of steel?" "A car". A Faraday cage is an example of something that blocks radio waves; it is not a generic term for something that blocks radio waves, and that's what the question is asking for. And a ferrite bead doesn't block radio waves; rather, it prevents the cable acting as an antenna. – David Richerby Feb 28 '17 at 1:54
  • @DavidRicherby The wire still acts as an antenna. The effect of the wire acting as an antenna is mitigated. The question has been appended since I answered it, and that makes my answer look a bit skewed now. There are several different ways no knock out RF from a physics point of view. The Faraday cage is a famous example of one of them. – Phil Sweet Feb 28 '17 at 2:59
  • @PhilSweet Even the original question was asking for a word for the concept, not the name of a specific device implementing that concept. "Faraday cage" isn't an answer to any version of the question that has been posted. And, OK, the ferrite bead decreases the wire's effectiveness as an antenna; but it doesn't "block" radio waves; rather, it causes fewer of them to be produced. – David Richerby Feb 28 '17 at 8:51
  • @DavidRicherby - You misunderstand electrodynamics. I up-voted this answer for mentioning the abstruse (to the layman) topic of ferrites and their role in attenuating electromagnetic waves. – Canis Lupus Mar 7 '17 at 19:54

I think you can just call it a Radio Jammer

  • 1
    That's what the relevant wikipedia article calls it. It also differentiates between jamming and interfering - a noteworthy distinction. Technical terms don't always sound eloquent or technical. – sleddog Mar 7 '17 at 19:53
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    Please edit your answer to quote a relevant definition of radio jammer from an authoritative source, and name the source. It could be a dictionary, or even Wikipedia, as Jonathan Reed points out. – Dan Bron Mar 7 '17 at 19:59
  • Jammers are active devices that interfere with radio reception equipment. The don't actually block anything. If you are trying to receive a radio signal, this is a distinction without a difference - your radio doesn't work. On the other hand, if you are trying to keep rf out of your gadget-that-isn't-a-radio-receiver, a jammer just adds to the problem. – Phil Sweet Mar 8 '17 at 0:29

Remember a wave of such or any such can only be amplified or weekend from the source or can be amplified and relayed from new energy but always expands and disperses. It can be covered up or altered through wave manipulation. Try Dispersial, Deflection, Disolvement, depending what your thingy, what in actuality it achieves.

  • Welcome to English Language and Usage. We are looking for answers that include references and citations. If you need assistance in framing an answer, please visit our Help Page on "How to write an answer" – Cascabel Mar 9 '17 at 4:02

The traditional word for blocking electromagnetic radiation is ‘jam’, used to describe interferring with radar in the second world war and its aftermath, but more generally since. The Oxford Dictionary on line gives the following as one meaning of jam used as a verb:

2.1 with object Make (a broadcast or other electronic signal) unintelligible by causing interference. ‘they were jamming broadcasts by the pirate radio ships’

So I would suggest that instead of looking for a noun, you might restructure your sentences to use ‘jam’ as a verb, which would have the advantage of general intelligibility.

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    The OP doesn't not appear to be talking about jamming (which does not block radio waves but swamps them with stronger signals). Rather he appears to be talking about some form of shielding. – Hot Licks Feb 27 '17 at 20:45
  • Yes, jamming is an active thing. OP is talking about a passive attenuation of the signal. – Jim Feb 27 '17 at 21:43

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