Ferrite Beads on A/V Cables: How Do They Work?

By Bobby Schweizer

Turns out that little plastic thing clamped to the end of our cables serves a very important purpose.

In our many electronic devices there are all sorts of doohickies and gizmos we take for granted, buttons we never think to press, and settings we never bother to change. And yet someone thought the function of any one of these things was important enough to include in the design.  

ferrite bead and it's a simple yet amazing little thing.  
 
help reduce radio wave interference in electronics. Most devices emit electromagnetic interference, but the casing of those appliances are designed to shield the radio frequency interference. Wires do not always have the luxury of being well shielded.
 
When a current passes through a cable it emits a small amount of electromagnetic waves which can travel into the attached device or computer. Given the intricate nature of all our electronics and their reliance on wireless frequencies of all scales, filtering out as much radio noise as possible is essential to their smooth operation.  
 
acts as a resistive impedance for high-frequency signals absorbing the extraneous radio waves and dissipating their energy as heat. Noise is filtered out before it can be transmitted into your computer. And not only do cords, cables, and wires transmit radio frequencies, they act as antennae as well.  
 
You know those annoying buzzes and beeps that GSM phones make when near a speaker? It's because the speaker cable is acting as a receptor for the wireless signal and is broadcasting the noise as annoying pops interrupting your favorite song or episode of This is Only a Test. While you can't do anything about the speakers in your TV or car, the problem can be resolved in desktop speakers by attaching a ferrite bead to the end of the wire.   
 
So now you can check off this little doohickie from the list of details we take for granted and use your new found knowledge to impress people at holiday parties.