dit-ditditdit-ditditdit-ditditdit
this post was submitted on 12 Sep 2025
432 points (98.4% liked)
Just Post
1139 readers
10 users here now
Just post something ๐
founded 2 years ago
MODERATORS
This interference was caused by RF (Radio Frequency) interference from the phone using GSM technology to communicate with the nearest cellphone tower. It would have been heard by any speaker you were close to. They stopped using this tech after 2g. 3g onward, you no longer heard this anymore.
I had Sony Ericsson Bluetooth headphones (12 years old) that somehow still picked those kinds of signals up.
Used as a party trick of late, as it catches most pings within 10+ meters. And breaks up completely when there are emergency services (police and firefighter squads) nearby.
We gave them to a local hacker club for laughs and giggles.
Not just GSM - any phone would do it, GSM was just more noticeable (I had a CDMA phone since 1996, all of them did this until about 2006).
Shouldn't a CDMA phone have caused the issue continuously then? They have a constance radio broadcast
GSM and CDMA don't really work that much differently. Neither has a constant-on radio, they register with a tower and then periodically check for a tower.
The main difference is one uses TDMA (GSM) and the other users CDMA for voice calls. (Time Division Multiplexing vs Carrier Division Multiplexing).
Text messaging is a side-effect of CDMA packet framing - it had to be tacked-on to GSM since it didn't utilize the same connection design.
Yeah I shouldn't have said constant I had that thought wrong. I guess it is better worded as continuosly syncratic rather than time based. I guess I was thinking the regular check-in would have caused the magnetic interference every time instead of just when the connection was amplified.
I thought TDMA would have died with 2g though. We have so many devices now I would think it would be impossible to have time slots for check ins. Sounds like something fun to look into but unfortunately I doubt I'll ever have time to play with that.
Always something new
I don't think it uses time slots for check-in, just for the voice call part. Especially since a phone changing towers wouldn't know what time slot was available.
I assume the interference is caused by a phone increasing it's power output to establish a voice call, which requires much more power than a data keep-alive/get messages connection.
It's been a long time since I did a deep dive though.
Was there only one model of speakers in the early 2000s?
No, there was also a black one.
subwoofer ๐
Woof woof
wait
The best thing about speakers was that they never seemed to die. I got a set of Logitech X-530 speakers in 2005 and haven't had a reason to replace them yet. Then again my monitor is from 2007 I believe.
If it ain't broke...
No, but maybe the one pictured was just the most common.
I had something similar to these, they had a "3D sound" button that just made the audio much louder.
Fun fact: in GTA IV, they had this effect if you were listening to the in-game radio and Niko got a phone call.
This is such a narrow slice of time and socioeconomic positioning when you think about it, but it feels universal.
Only a handful of people will have ever lived in the intersection between shitty, leaky phone connectivity and shitty, flimsy PC speaker shielding while having enough money to own both at any point.
My Fender Stratocaster did the same thing. Also if you wore a quartz watch you had a free 60bpm metronome when it was near the pickups.
Love the connection you draw!
Fun story about that, back when these were popular and cell phones interacted with them, I was working with a band called "Matt Hates the Box" and they had a really good take of some recording, but a text message came in and over-wrote on the recording the beeping modulation sounds.
I was able to rescue the take because the modulation was a very specific pulse of tones, so I went in and EQ'd out the beeps and we were able to keep the recording on the record as is minus that one minor change.
This is always the memory that comes to mind every time I'm reminded of this phenomenon.
It was cool, you could put your phone on silent but still get a notification it was ringing from across the room.
It still perfectly works. I have a pair of speakers and right before my phone ring I hear that sound. Even if it's not my phone.
I still have one of these somewhere. It will play a local radio station if I hold the back of it. The volume dial does not affect the volume of the radio signal.
I have an old set of Dell speakers (5.1 setup) that I got with my computer back in 2004 and they still work great. The only problem is that I moved about a mile away from a radio station, so now I can hear it when no other audio is playing. Ferrite beads helped immensely, but not 100%.
I can hear this photograph
I had those exact speakers for like 20 years before one of them finally crapped out and I had to get more modern ones.
Also, ATM0 unless you like the sound of WEEEEEEoooWEoWEEEEEEEEEEEEEEESCREEEEEEEEEEEE
I dont know why but I liked hearing the connection sound. It made sure no one picked up the phone in the time you checked the phone to check and when you initiated the actual connection.
ATM0?
I'll leave that as an exercise for the reader.
TIL those codes
The modem's speaker is always off
Hayes, I see what you did there.
Is that actually the sound the speakers made?
I had the speakers in OP but didn't get a cell phone until the OG Droid
Yeah, but I remember it being much worse. It'd do that 'bupadup bupadup bupadup' then launch into a digital scream right when the phone started actually ringing.
Around the 3:20 mark, this video shows the more full effect.
How did this work
Poor shielding. So when a nearby phone sent out radio bursts to reach say the cell tower, it would case the speakers to pick up the bursts.
Speakers manufacturers now know wireless devices will be all around their devices, so they shield them better.
I think the eMachines eOne (that iMac G3 knockoff) playing a weird buzz sound when Windows is running might also be related to poor shielding, but I could be wrong about this.
The electronics in the speaker's internal amplifier resonating to a frequency of old 2G GSM signals and then amplifying that interference. It happened with cheap speakers because as the other person pointed out, they were poorly-shielded, if at all.
Magnets.
I still sometimes hear this if my phone drops fron 5G and I am around a really cheap speaker.
Yeah this can still happen if your phone so happens to connect to an old 2G GSM tower. They've been phasing them out for years, but there's still plenty of them in lesser-populated areas because it's reliable and you don't need to have as many towers to get a good signal.