In analogue times, this sometimes resulted in hearing the actual audio content of radio chatter, often on public PA systems, which were sensitive to stray radio frequency emissions. Radio manufacturers try to minimise sensitivity to “out of band” frequencies, but a strong signal can cause a response. It is possible to use something called a ferrite choke to suppress this – that’s what the cylindrical object you often see on power cables for laptops is. Electric guitar players are all too familiar with this effect: if they stand next to any device with a conventional transformer there is a loud hum through the amplifier their guitar is plugged in to.Ĭomputers are another source of electromagnetic interference because the processor is operating at gigahertz frequencies too. What you are hearing is the burst of phone signals at gigahertz frequencies being modified by the electronics in the radio.Įlectromagnetic interference can be picked up from other devices, too, such as the motors in vacuum cleaners and power drills.
The same effect allows wireless charging of small electrical devices like toothbrushes. Later mobile phone standards use a different form of location update, so you will hear this sound only when the phone is using the GSM network, usually because of lack of coverage on the 4G network.
PHON AUDIO TUNER SERIES
The complete location update, as defined in the Global System for Mobile communication (GSM) specification, consists of bursts of transmissions with set timings between them, and this gives a characteristic series of sounds. This is needed so the phone network knows which base station should contact the phone in case of an incoming call. The most typical sound is generated during a location update.
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