If I have my boxes on on my computer – separate boxes, not built into my laptop – and I get a text message, I hear that familiar beeping. How come? Radio signals that are disrupted are not possible, because I am not listening to radio at that time. Does it have something to do with a magnetic field from the cell phone radiation that affects the current in the wires?
Answer
Best,
The signals that a mobile phone receives and emits are electromagnetic waves, which, as the name suggests, have both an electrical and magnetic component. When receiving an SMS, the electromagnetic field strength is therefore large and will be absorbed by the winding of the sound coil of your loudspeakers. It is essential that the incident magnetic field varies with time to create a voltage in the winding via induction
. This changed voltage will thus induce a current that makes the diaphragm of your speaker vibrate = noise. However, the electromagnetic wave of your mobile phone vibrates about 2 billion times per second, while the sound (via acoustic waves) that we hear only vibrates a maximum of 20 thousand times per second. The diaphragm of your speakers can’t vibrate that quickly and that’s why we only hear some noise.
If these loudspeakers were built into a metal packaging/cage (= Faraday cage) then no noise will be produced by the loudspeakers, as the electromagnetic waves cannot propagate through a metal shield.
more information about electromagnetic induction can be found on the following webpage:
http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.html
Answered by
Micro and Optoelectronics Semiconductor Physics Semiconductor Technology
Free University of Brussels
Avenue de la Plein 2 1050 Ixelles