What's the physics behind this phenomena (sound / electromagnetics)

In summary, sound is a mechanical wave that requires a medium to travel through, while electromagnetics are waves of electric and magnetic fields that can travel through a vacuum. They both require a source of energy to initiate the waves, and their interactions with matter differ. The speed of sound and electromagnetics also vary, with the speed of sound depending on the medium it is traveling through and the speed of electromagnetics being constant in a vacuum. In everyday life, sound is used for communication and entertainment, while electromagnetics are used in various technologies and medical imaging techniques.
  • #1
nietzsche
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I have a stereo set-up with a sub-woofer. Sometimes, if my laptop is plugged in close by or in the same outlet, the sub-woofer "hums". It's not like a rumble, it's like a long, low, note.

An engineering major told me that it had something to do with magnetic fields being generated or something, but I wasn't entirely sober when he was explaining it to me. What could be causing it?
 
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  • #2
Electromagnetic interference, most likely. Probably conducted EMI.
 
  • #3


The phenomenon of the sub-woofer humming is likely due to electromagnetic interference (EMI) caused by the close proximity of the laptop and sub-woofer. Both electronic devices emit electromagnetic fields, and when they are in close proximity, these fields can interact and cause interference. This can result in the sub-woofer producing a humming sound.

The specific physics behind EMI involves the principles of electromagnetism, specifically Faraday's law and Lenz's law. When an electronic device, such as a laptop, is plugged in and turned on, it creates an alternating electromagnetic field around it. This field can induce a current in nearby conductors, such as the wires of the sub-woofer, causing it to vibrate and produce sound.

Additionally, the electrical wiring in the walls and outlets can also contribute to EMI. If the laptop and sub-woofer are plugged into the same outlet, the wiring in the walls can act as an antenna for the electromagnetic fields, further increasing the interference.

There are ways to mitigate EMI, such as using shielding materials or keeping electronic devices at a safe distance from each other. It is important to be aware of EMI and its potential effects, as it can impact the performance of electronic devices and potentially cause damage. Overall, the humming sound from the sub-woofer is a result of the complex interaction between electromagnetic fields, and understanding the physics behind it can help in finding solutions to reduce or eliminate the interference.
 

1. What is the difference between sound and electromagnetics?

Sound is a mechanical wave that requires a medium to travel through, while electromagnetics are waves of electric and magnetic fields that can travel through a vacuum.

2. What causes sound and electromagnetics to travel?

Sound travels due to vibrations in the medium, while electromagnetics travel due to the changing electric and magnetic fields. Both require a source of energy to initiate the waves.

3. How do sound and electromagnetics interact with matter?

Sound waves can be absorbed, reflected, or transmitted by different materials, while electromagnetics can be reflected, refracted, or absorbed depending on the material's properties.

4. What is the speed of sound and electromagnetics?

The speed of sound depends on the medium it is traveling through, with an average speed of 343 meters per second in air. The speed of electromagnetics, specifically light, is constant at approximately 299,792,458 meters per second in a vacuum.

5. How are sound and electromagnetics used in everyday life?

Sound is used for communication and entertainment, while electromagnetics are used for various technologies such as radio, television, and cell phones. Both are also used in medical imaging techniques like ultrasound and MRI scans.

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