EMI Shielding

EMI, or Electro-Magnetic Interference is radiated by every single electrical or electronic component inside your computer. The interference takes the form of radio waves, ranging in frequency from a few Hz right up into the GHz range. This interference can be picked up by almost any electronics, as every piece of wire is a potential aerial.

You may have experienced the effects of EMI if you have got bad reception on a radio when it is near a computer, or heard your speakers make noises when a nearby mobile phone receives a text message. Analogue circuits, especially audio ones, are the most sensitive to EMI.

This means that shielding your computer as well as your audio cables is a good idea, if you have a lot of audio equipment. Your case forms a conductive box around your PC, Called a Faraday Cage, trapping and suppressing the interference. Unfortunately, any hole, or non conductive part in the case can give the interference a place to leak out, making the case completely ineffective. This is why cases have metal blanking plates behind the CDROM drive bays.

The AcoustiCase is one of the rare cases that actually pays some attention to EMI issues. There are strips of copper along the edges of each card slot, effectively eliminating any electrical gap. Both pictures below show little contacts along the edges of the case, which make electrical contact with the side panels. These shorten the length of the cracks around the edges, and restrict the number of wavelengths that can pass through these cracks. Long gaps in the electrical continuity will leak interference no matter how thin they are. The fan cut-out at the back is made up of lots of small round holes. This means that only interference with a wavelength small enough to pass through the holes can leak out. The metal mesh inside a microwave door does the same thing.

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