Why Are My Speakers Humming/Buzzing? (Electrical Interference)

Why Are My Speakers Humming/Buzzing? (Electrical Interference)

Electrical interference is when high-frequency signals induce a voltage onto an analog signal. This can cause incorrect readings or errors on the analog device. The effects of electrical interference can be minimized with the help of a number of techniques. Most often, these electrical noise reduction techniques include proper shielding, filtering, grounding, and cable isolation techniques.

1. Electrical Interference Shielding

This means using a physical barrier (usually made of conductive material), to reduce or block unwanted electrical signals. Commonly used materials for electrical interference shielding include: metals such as aluminum and copper or steel, conductive foams and fabrics, conductive coatings and paints, and even conductive elastomers.

  • For electrical noise shielding that requires or will work best when you block the electric field of the wave, use a material with high conductivity.
  • To reduce the magnetic component of the radiation, use a material with high magnetic permeability such as carbon loaded rubber or ferrite.
  • It’s also good practice to reduce the number of holes in your shield that could serve as entry and exit points for the radiation and use conductive sealing gaskets as needed.
  • If weight or cost is an issue, a plastic shield with conductive coating may be used.

2. Electrical Noise Filter Circuit

This involves adding electrical filters to the power or signal system with the aim of removing unwanted signals, dissipating them, and preventing them from entering the system. Commonly used electrical noise filter techniques include inductors, capacitors and ferrite beads.

  • An electrical noise filter can be placed on the device that requires protection, or outside but close to it.
  • If filtering analog signals, it’s usually necessary to amplify them before the filtering stage.
  • The electrical noise filter circuit must be tuned to block out the frequencies associated with the interference, while still allowing through desired signals.
  • Ensure the right type of filter for your circuit, or it may not provide the required effectiveness.
  • Filtering is also often used together with other methods of attenuating interference, such as shielding and grounding.

3. Grounding Noise Reduction

In order to prevent electric fields from causing interference, it’s crucial to ensure that all electric circuits are properly grounded. Grounding noise reduction works by providing a path for the flow of electric current away from sensitive components back into the earth or other conductive materials.

  • Grounding noise reduction works best if the conductive path is of very low impedance.
  • To reduce inductance, therefore, keep leads as straight and short as possible.
  • Consider separating analog and digital grounds to further reduce the potential for interference.
  • Use grounding to suppress the electrical noise of signal cables whenever necessary.
  • When a shielded cable forms part of the signal’s return path, consider grounding it on either ends. If not, you’ll only need a single ground.

4. Proper Routing of Cables

Proper routing of cables is one of the ways of reducing electrical interference from external sources. It ensures that signal and power lines are not routed close to each other, for example, thus reducing the potential for interference.

  • To reduce the risk of external interference, it’s best to route cables away from sources of noise such as radio transmitters or other electrical equipment.
  • If you must route wires in close proximity to sources of interference, ensure they’re properly shielded.
  • For signal cables, you may consider using twisted-pair cables for better electrical noise suppression.

Electrical interference can be very disruptive and costly when it reaches electronic devices. However, with proper engineering techniques such as shielding, filtering, grounding and cable isolation, this interference can be minimized or eliminated. We hope this guide has been helpful in providing an understanding of the causes and solutions to electrical interference.
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