Ferrite Beads: What They Do, How to Install Them, & More

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Easily reduce electronic interference with ferrite beads

Co-authored by wikiHow Staff

Last Updated: October 30, 2025 References

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Why Use Ferrite Beads

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Buying Ferrite Beads

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Installing Ferrite Beads

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FAQ

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Video

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Tips

If you hear a high-pitched hum, hiss, crosstalk, or high-frequency sound come through your speaker or headphones when you plug them into a computer or stereo, you’re hearing radio frequency interference. To filter that high-frequency noise, you can use a ferrite bead–a small contraption that wraps around the cord close to the power source. Read on to learn how to choose, buy, and use ferrite beads to reduce interference and get clearer audio.

What Do Ferrite Beads Do?

Ferrite beads, also known as ferrite clamps or chokes, are small devices that suppress radio frequency interference (RFI) in electronics. If you hear a high-frequency hum, hiss, or crosstalk from speakers or other electronics, clamp a ferrite bead around the cord about 2 inches (5.1 cm) from the device it connects to.

Section 1 of 4:

Why use ferrite beads?

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Use a ferrite bead to minimize radio frequency interference (RFI). If you hear a high-pitched hum, radio broadcast, strange speech, or some other bizarre high-pitched noise when you turn on your laptop, use your headphones, operate your radio, or plug in your guitar, you’re experiencing RFI. This means that another device–a radio, cell phone, walkie-talkie, fluorescent light, or even a power line–is interfering with the frequency of the device you're trying to use. To reduce the noise, you can attach a ferrite bead (also known as a ferrite choke, ferrite ring, or ferrite sleeve) to the cord.^{[1]
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- Ferrite beads can be used on all kinds of electronics. Laptops, headphones, stereos, guitar and bass amps, headsets, gaming systems, radios, and televisions are likely to experience RFI and could benefit from a ferrite bead.
- Using ferrite beads on audio cables, HDMI cables, instrument cables, and even USB cables will prevent devices from picking up RF noise.
- Ferrite beads also reduce electromagnetic interference (EMI).^{[2]
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Install a ferrite bead or core internally if you’re building your own hardware. If you build your own electronics and want to reduce RFI, you can install a ferrite bead or core in the internal wires. This is a more complex procedure that involves knowing the hardware’s voltage output as well as the heat dissipation.^{[3]
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- The manufacturer of the ferrite bead should be able to give you information about the impedance versus the load current curves. This can help you choose the right kind of ferrite bead for your project.

Section 2 of 4:

Buying Ferrite Beads

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Choose the size of the ferrite bead based on the thickness of the wire. Thin cords, like headphone cords, need a 3 mm (0.30 cm) bead. USB cables and network cables will need a 5 mm (0.50 cm) bead. Thicker computer, electronic, or instrument cables will need a 7 mm (0.70 cm) bead. Power cords will use a 9 mm (0.90 cm) bead, and 120-volt power cords or 12-gauge cords will take a 13 mm (1.3 cm) bead.^{[4]
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- If you buy a ferrite bead that is too big, you can loop the cord around it to make it fit more tightly.^{[5]
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Buy ferrite beads online or at an electronics store. You can often buy a variety pack of beads on Amazon or at an electronics store so you have multiple sizes to choose from. Make sure to buy ferrite beads that clip closed rather than ferrite cores, which don’t have a hinge.^{[6]
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- Ferrite cores are most often used in internal hardware design. They’re installed before the actual electronic is finished and aren’t usually seen by consumers.

Section 3 of 4:

Installing Ferrite Beads

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Place the bead on the cord about 2 inches (5.1 cm) from the source. The bead should work regardless of its position on the cable, but it may work better at reducing RFI if placed closer to the source. It can even go up against the device without hurting anything.^{[7]
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- For example, if you're using a ferrite bead or choke to reduce noise from your headphones, place the bead about 2 inches (5.1 cm) from the device your headphones are plugged into.
- Test the ferrite bead at different positions along the cord. If you hear less noise at a specific point, use that location.
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Bend the cord into a loop first if it’s too loose on its own. Take the cord and fold a 2 to 3 inches (5.1 to 7.6 cm) section over on itself so it’s twice as thick. If you want, you can loop the end of the cord back so that it’s three times as thick and pointing in its original direction.^{[8]
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- This will help keep the ferrite bead in place and press it more firmly against the cord, which means it’ll do a better job at reducing the RFI.
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Clamp the ferrite bead closed. Once the bead is in place, close it and press the two sides together until you hear them click into place. Gently pull at both sides to check that it is securely in place on the cord.^{[9]
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- You don’t want the bead coming loose and falling off the cord, especially if it’s in a hard-to-reach place.
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Use a space filler if the ferrite is still too loose on the wire. Hold the cord up and check to see if the bead stays in place. If it slides down the cord and you can’t loop it again to make it fit more tightly, use something like a toothpick, plastic paperclip, or bobby pin to fill the extra space.^{[10]
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- The ferrite bead will still work even if it is loose, but it may not work as well as it could. Keeping it in place and tight against the wire is the best way to consistently reduce noise.
- Avoid using a metal paperclip, as it could potentially interfere with the effectiveness of the bead.

Section 4 of 4:

FAQ

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When should I use ferrite beads? If your powered speaker, guitar amp, headphones, or any other powered electronic devices emit a high-frequency hum, static, or other interference, a ferrite bead will help reduce or eliminate the noise.^{[11]
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Do ferrite beads actually work? Ferrite beads work to suppress RF and electromagnetic interference. However, they'll only block out high-frequency interference. If you hear a low-frequency hum, or if there's a grounding issue, a ferrite bead won't fix the problem.^{[12]
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What is ferrite? Ferrite is a ceramic material made of iron oxide, zinc, manganese, and other metal oxides. Because of their metal content, ferrites have high permeability to magnetic fields and high electrical resistance.^{[13]
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Where do you put a ferrite device for a power cord? Install the ferrite bead or choke about 2 inches or so from where the cord connects to the device. You can install it closer to the device if you'd like, and it won't cause any problems.

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Tips

Chances are, you’ve seen a ferrite bead or core in your own home and just didn’t know what you were looking at. If you have any wires that look like they have a small box on them close to the plug, that small box is a ferrite.

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