Why wireless radios start making buzzing noise when I switch on some electrical appliances? This question has possibly been asked a numerous number of times already, by many people in many places, but nowhere can I find a precise answer to my precise question.
When I turn on, say a ceiling fan or any other electrical instruments near a wireless radio (I don't know what happens with mobile phone radios), it starts making a buzzing background noise. Sometimes it only makes a momentary "thud"-like noise - similar to what happens inside the fan switch (we can see a momentary electric spark, due to a reverse current of the inductor coil) - when you turn a ceiling fan or a light on or off.
Also, talking over a mobile phone while staying close to the radio makes an 'extraterrestrial' noise in it. (Sometimes when there is a live talk show on the radio, and someone calls there through their mobile, and while talking to them they sit close to their radio set, most probably to simultaneously talk and hear their own voice over the radio. But everyone listening to that frequency can hear that extraterrestrial sort of bouncy noise! And the anchors over there at the broadcasting centre asks the caller to move a bit far from the radio set.)
There are battery powered radios and electrically powered ones. But the second ones continuously makes a buzzing noise if you listen carefully.
Why?
 A: Unbound accelerating charges emit electromagnetic waves.
The general term for the noise produced due to unwanted electromagnetic waves is radio frequency interference, rfi.
The 50/60 Hz mains supply with electrons oscillating in the cables produces electromagnetic waves of frequency 50/60 Hz which can sometimes be picked up as a background mains hum which may well be the source of your continuous buzzing noise.
Sparking with charges being accelerated within the spark  produces a whole spectrum of electromagnetic waves which can be picked up by radios, more so by non-digital ones.  This can well be the source of interference originating from your fan.  There was a time when the spark produced a useful emission of electromagnetic waves -  the spark-gap transmitter has a tuned circuit so that a resonance effect produces a predominance of electromagnetic waves with a relatively small frequency range.
Turning on a fluorescent light produces electromagnetic waves due alternating currents passing though an inductor in the starter circuit which is used to initiate the discharge through the tube.
Electrical power lines produce audible sounds and well as radio frequency interference due to corona discharges around the transmitting cables.
One reason for moving to sending radio and other signals digitally is to reduce and often eliminate rfi.
Computers and mobile phones (which have microprocessing chips within them) produce both wanted (eg Bluetooth, Wifi etc) and unwanted electromagnetic waves some of which can be picked up on a non-digital radio.
