I went to community college in the early 00’s when phones really started to take off, and I distinctly remember whenever watching anything video related on a CRT TV multiple times while watching TV there would be the distinct sound of interference, it sounded like loud beeping but in a distinct pattern. I only learned later that was the sound of interference from a cell phone signals, and you can still do it (but only intentionally) at least for myself by putting a cell phone directly next to a set of speakers playing something else and receiving a text message or call. But during the day nobody would be anywhere near the TV and you’d hear the sound of interference constantly.
So what happened, was it a CRT problem, or did TV’s just get better shielded or cell phones stopped being so noisy?
Are you talking about this noise? I recall, back in the 90’s, that sound coming out of computer speakers, IIRC, just before the phone would ring. I know you can also hear it on TV shows recorded in the 90’s, indicating to me, someone (actor? editor? sound engineer?) probably had a phone on them causing the noise and didn’t realize it was happening.
As for why it doesn’t happen anymore, my WAG is that it’s due to newer (at the time) network tech. ie GSM vs 3G.
I believe that the main reason is that today’s cell phones operate on much higher frequencies and additionally, at lower power much of the time. They use the minimum power required to reach the nearest cell site.
There are probably numerous factors including changes in cell phone technology as noted, but keep in mind that back in the early 00s most television broadcasting was analog, which was subject to all kinds of interference. It’s been all digital in the US since 2009, using the digital ATSC standard instead of the old NTSC. That alone would have made a big difference.
I’m not sure this was cell phone interference. Cell phones would periodically communicate to the towers which was basically the tower and the phone talking to each other enough to figure out that the phone was still inside that cell, but this would show up as occasional chirps and not as constant noise.
Newer communications technologies do cause less interference, so this is part of it, at least for things like amplified speakers. You can still get cell phone noise out of amplified speakers these days (as the OP notes) but you don’t get as much interference as you used to.
This is the main thing, though. With old fashioned analog signals, any noise would get mixed into the signal. The sound channel on NTSC was FM encoded which gives it some noise immunity, but all of the circuitry to decode the sound was analog.
With modern TVs, everything is digital. There is still some analog circuitry as you basically still have an analog amplifier driving the speakers, but everything before that is digital.
Digital signals are much more immune to noise than analog signals since with digital signals if you don’t get enough noise to completely flip bits then the noise is completely 100 percent rejected.
According to the Wikipedia article on TDMA the speaker interference was(is) a result of that technology. Most 3G is not TDMA, so along with the technological advances reducing signal wattage substantially, that could explain the end of cell phones interfering with your speakers.
Awww, everyone beat me too it. But yeah, it is still an issue depending on your equipment. I have an old set of speakers in the house (since lent to my wife when I upgraded) that have this irritation inducing flaw. It was rarely a problem for me when I was using them, since the distance between my speakers and the phone in my pocket was sufficient to reduce the interference. My wife though puts her phone on the desk while using her computer, and at only 1-2 feet from the old speakers, it is a regular occurrence.