Back in the day when mobile phones were around audio speakers, the speakers would emit some sort of crackling/static a few seconds before any call came in. This does not seem to happen these days. What has changed in the phones or speakers or both for this to not occur anymore?
In: Technology
back “in the day” of 2 and early 3g phones, the signal spectrum needed a significantly more powerful signal to get the phone to ring.
your phone would listen for a radio signal telling it there was an incoming call.
it would then turn on it’s onboard amplifiers, and start to amplify that signal, as well as to send a signal to the nearest cell tower saying “i’m here, and i’m answering”.
the series of pulses you would hear on speakers was the interference from those outgoing signals.
modern day mobile phones (4 and 5g) firstly use a much higher frequency spectrum, so any pulses you would possibly hear would be significantly faster, and higher pitched, and secondly need much less powerful signals, so if you did hear them, they’d be a lot quieter.
plus new mobile phones transmit much more tightly attenuated signals, which modern speakers can be fairly easily shielded against by simply including a ferrus coil somewhere inside.
tl;dr modern phones make much less electrical noise when they answer, and modern speakers are better sheilded.
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