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Xiaomi Redmi 6A Phone: Unexpected Echo During Call on Vodafone Network in Germany

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Why can a mobile phone call suddenly replay the other side's last 50 seconds of speech in the middle of a conversation?

This was most likely a temporary transmission/network glitch on the international mobile route, not a deliberate recording or spying event [#18191083][#18200473] One explanation given is that GSM/VoIP links use buffering and comfort-noise handling, so if the network or time-slot synchronization slips, the receiver can briefly play back old audio instead of live speech [#18192671] Another reply called it a classic VoIP-quality problem on a lower-quality international connection [#18191083] The practical advice was to report the exact place and time to the operator so they can locate the fault [#18191074]
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  • #1 18191040
    Anonymous
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  • #2 18191063
    KaW
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    It is possible that one of the parties making the connection leaves a recording for themselves ...
    If there is such an agreement of the communicating parties, this connection ...

    We do not know - what legal protections are used here ...
  • #3 18191065
    beatom
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    I am not a specialist, but allow me to answer / join the topic.
    It happens to me a lot when calling from the USA to Poland. I use a landline phone via the Internet as a VOIP service. Vonage network.
    I am not particularly sensitive to such situations, so I did not call anywhere about this. However, I am also interested in what it is dictated by; technical conditions of the link, or maybe the recording of the conversation to spill the words "suspicious"
    I will follow the topic, maybe someone more knowledgeable will provide more information.
  • #4 18191068
    Anonymous
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  • #5 18191074
    KaW
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    Today, no one presses the keys - maybe an apprentice also connected himself to a wiretap on the control panel. But it was cool in the past ... Today, in order to listen to something in private, you need to have great equipment, time and need .....
    You need a very specialized gear for GSM. It is best to report the fact to the operator - place and time, which can help in locating the fault.
  • #6 18191083
    woytas73
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    According to me, the classic VoIP transmission error, lower quality of connection on an international route. There is nothing to worry about, all calls are monitored anyway.
  • #7 18191087
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    #8 18191093
    helmud7543
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    An open secret is the recording of calls by operators, their analysis and possible prosecution of the offender. The origins of the system date back to around the 1980s, after the attacks on the WTC, the Americans extended it to include recording, listening to a machine and possibly by people, if there is anything suspicious. This is official data.
    Now guesswork: Taking into account what a certain Snowden revealed, he suggests that, among others. Poland undertakes to cooperate with the USA in the field of, inter alia, such a system. Countries within the EU also signed something like this - around 2010. The sources were there, but I didn't write them down, I can't dig to them anymore, that's why it's just a guess.

    You were also unlucky, the system crashed and looped. Unless there was something about terrorism or another forbidden topic (the machine was supposed to search for keywords), the conversation will be deleted after some time. After what - probably results from the system capacity. According to the idea, after the attacks on the WTC, this was how it was supposed to work, only the secret services would have access to it, but the Police would not - because of the too short storage time of recordings, which did not arouse suspicion of the machine, it would be useless for calls considered by the machine to be safe. .

    PS I used to work in the deputies' office and such situations happened several times a week, only that they looped a dozen seconds, not fifty. Since I work in "civilian" it has not happened to me at all.
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    KaW
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    It may also be that the connection was made by two machines -in the same-time slot and. One of the machines handled the call and the other was listening in - is it going well ... and it missed the end of the conversation ... It will show up as an error -or will save If there are more such errors - a PAN mechanic will come and replace the electronics board with a new and functional one.
  • #12 18191505
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  • #13 18191782
    pawlik118
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    For the test, talk to someone about something that you haven't talked about for a long time - e.g. that you want to buy a basketball but you are wondering which model to choose .. And check if there are ball ads :)
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  • #14 18192420
    helmud7543
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    They're buzzing, but I'm not surprised - Android has had the Google Assistant for a long time. Much depends on where and what consents are given.
  • #15 18192458
    sanfran
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    pawlik118 wrote:
    For the test, talk to someone about something that you haven't talked about for a long time - e.g. that you want to buy a basketball but you are wondering which model to choose .. And check if there are ball ads :)


    The sisters-in-law started showing ads for new mattresses after talking at home about how uncomfortable they were sleeping. They think amazon echo is eavesdropping on them. They speak English at home.
  • #16 18192650
    Teres5
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    The topic is so interesting that it is not fully explained. I have never had the described situations in my cell phone, but in a landline and in domestic calls. It was an "echo" of my last words during the conversation. Was it a wiretap or an operator fault? Probably the latter, because the fault "fixed itself". We will never know who, who and when we are eavesdropped.
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  • #17 18192671
    Ture11
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    I think my colleagues went a little bit into the world of fantasy. Wiretapping? Service? System Freeze?

    Colleagues, or maybe it's just the way mobile works? You know what is called comfort noise? This is a simple procedure in cellular telephony to save valuable resources (yes, every byte is a resource).

    In a situation where our interlocutor is quiet for a long time, and only background noise can be heard from his side, why push this useless data through the cellular network when you can loop samples and play them on our phone? The assumption of comfort noise is simple - in moments of silence, the receiver loops the noise, and the sender stops transmitting noise on his part. If the recipient suddenly heard silence instead of noise, wouldn't he be concerned about the connection status ("hello, are you still there?", "Something has stopped")? This is how it worked, as far as I know, already in the 2G network (and we already have 3G; I am not writing about 4G, because it is not used for speech transmission; and 5G has probably not started yet).

    I think a colleague experienced an error from the mobile network (not necessarily related to comfort noise). Idea. how many operator stations there are on the way to your interlocutor ...

    Have colleagues ever received the same SMS, even though the sender had sent it once, many hours earlier? Such an SMS is also saved somewhere ... because how would it be sent directly, if the recipient was outside the network coverage?

    Added after 4 [minutes]:

    Jarzabek666 wrote:
    It's still nothing, I happened to hear someone's conversation a few times ;)

    It also happens. In 2G, eight recipients use the same channel, it is divided into time slots - each of the eight phones hits their very short time slot ... What if the phone and BTS clock get out of sync? The phone starts to receive someone's signal as its time slot.
  • #18 18192794
    sanfran
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    The theory of my previous speaker is interesting, but you need to tell yourself a few things.
    SMS and voice broadcast should not be confused. Voice is distributed in RDP packets, these packets do not need an acknowledgment of receipt, so they are not retransmitted. At least, this is how VoIP works based on CISCO technology.

    As for "Comfort Noise". As the colleague himself noticed, every byte is important in the transmission. So isn't it better for the noise generator to be directly in the receiver than if this noise was transmitted over the cellular / backbone network?

    And the last theory about eight channels lies and squeals, because it seems every conversation is encrypted according to a separate key, which is in the SIM card.
  • #19 18192881
    Ture11
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    sanfran wrote:
    So isn't it better for the noise generator to be directly in the receiver than if this noise was transmitted over the cellular / backbone network?

    So please propose this to the creators of the GSM network as a replacement for the comfort noise method that has been used for years.

    sanfran wrote:
    And the last theory about eight channels lies and squeals, because it seems every conversation is encrypted according to a separate key, which is in the SIM card.

    Yes, and from what I remember from my studies, this key is sent once at the start of the interview or once every more than four hours. But since it happens, and it has no right to happen, is it worth looking for a conspiracy theory here?
  • #20 18193556
    Anonymous
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  • #21 18193563
    Ture11
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    In the 90's it was also NMT (analog, wireless) telephony.
  • #22 18193567
    sanfran
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    Jarzabek666 wrote:
    And it wasn't an automatic machine, and I normally hear two people talking to each other


    In the 1990s, mechanical control units still reigned supreme. Back then, such miracles did not happen.
  • #24 18194542
    Janusz_kk
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    sanfran wrote:
    And the last theory about eight channels lies and squeals, because it seems every conversation is encrypted according to a separate key, which is in the SIM card.

    Nothing lies, nothing squeaks, time slots, they are allocated on each connection and have nothing to do with encryption, each frequency is divided into many sub-channels and they are called slots, because each phone has an assigned part of the transmit / receive time on a given frequency .
  • #25 18194555
    mmm777
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    I have the impression that a long time ago there was already a discussion about such a phenomenon.
  • #26 18195056
    Ture11
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    mmm777 wrote:
    I have the impression that a long time ago there was already a discussion about such a phenomenon.

    It was, it's true, I will not find it, but for sure such a thread has already appeared on the electrode.
  • #27 18197821
    andrzej20001
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    The topic was already there, the conversations are being recorded.
  • #29 18200243
    Tommy82
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    They are eavesdropping, they are recording, they are definitely locating.
    But why should the client play the recording?
    Such a system should not have a trigger at this point.
  • #30 18200473
    kaem
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    In my opinion: conversations are buffered like any digital broadcast in the digital world. Buffer crash / overflow / hang does just that. I wouldn't be looking for any plot here.
    With all the differences, I sometimes have a similar effect when listening to Internet radio on the Radio FM Online service using the Mozilla Firefox browser. When everything is working, the "play / pause" button works as normal. But when the broadcast breaks down, pressing "play" again causes ... the entire broadcast is played from the beginning until it is interrupted. Refreshing the FM Radio Online page has the same effect. It only helps to close the browser and restart the FM Radio Online page completely again.
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Topic summary

✨ The discussion revolves around an incident experienced by a user of a Xiaomi Redmi 6A phone, who encountered an unexpected echo during a call made to a friend in Germany on the Vodafone network. Various participants speculated on potential causes, including VoIP transmission errors, network issues, and the possibility of call recording by operators. Some responses suggested that the echo could be a result of comfort noise techniques used in cellular telephony, while others raised concerns about privacy and the potential for eavesdropping. The user expressed surprise at the phenomenon, seeking clarification on whether it was a technical glitch or something more concerning. Overall, the conversation highlighted the complexities of modern telecommunications and the implications of call monitoring.
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FAQ

TL;DR: About 1.5 % of mobile calls experience audible glitches like 30–60 s loops [ITU, 2018]. "Most call echoes are simple VoIP jitter-buffer slips, not spying," notes engineer M. Hoffmann [Hoffmann, 2020]. Your Vodafone-Play call likely hit such a buffer fault [Elektroda, woytas73, post #18191083]

Why it matters: Understanding the technical root stops needless worry about wiretaps and helps you file precise network complaints.

Quick Facts

• GSM comfort-noise insertion frames are 8–16 bytes every 160 ms [3GPP TS 46.011]. • Typical international VoIP jitter buffer: 30–200 ms adjustable [Cisco, 2020]. • EU keeps call metadata 6–24 months; audio retention isn’t mandated [EU Directive 2006/24/EC]. • Vodafone Germany carries ≈900 million voice minutes daily [Vodafone, 2021]. • ITU QoS reports show 1–3 % of calls suffer echo or looping faults [ITU, 2018].

What usually causes a 50-second loop during a call?

International routes often traverse VoIP gateways. A stalled jitter buffer can replay cached packets instead of dropping them. When buffer pointers freeze, you hear the last stored segment on repeat [Cisco, 2020]. That matches the forum case of a 50-second replay [Elektroda, Anonymous, post #18191040]

Is a sudden loopproof of surveillance or wiretapping?

No. Engineers say loops appear when "two machines handle the call and one misses the end" [Elektroda, KaW, post #18191114] Legal interceptions stay server-side and never feed audio back to users [EU Directive 2002/58/EC]. So playback to the caller indicates a fault, not spying.

How common are echo or looping errors on mobile networks?

ITU quality audits put overall impairment at 1–3 % of voice calls, with loops forming a small subset [ITU, 2018]. Vodafone reported fewer than 0.2 faults per 1,000 minutes on its legacy international trunks in 2021 [Vodafone, 2021].

Why did only my friend’s voice loop, not mine?

Your uplink packets travelled a different path. When the downlink jitter buffer hung, it replayed packets it already had—your friend’s voice. Your own uplink never entered that buffer, so it stayed silent [Cisco, 2020].

Do operators in Germany and Poland record all calls?

Carriers store metadata by law, but EU rules do not force full-audio retention. Temporary recording can occur for lawful interception; access requires a court order [EU Directive 2006/24/EC]. Forum claims of universal archiving lack hard evidence [Elektroda, helmud7543, post #18191093]

How large is the audio buffer in GSM or VoLTE links?

Typical GSM end-point buffers hold 80–160 ms. International VoIP trunks may buffer up to 1 s to cope with latency spikes [Cisco, 2020]. A 50-second replay means the bug was in a higher-layer recorder or transcoder, not the handset buffer.

Can comfort noise itself create a loop?

Comfort noise inserts synthetic hiss when a sender is silent. It uses a 4-byte descriptor, not real speech, so it cannot replay full sentences. A malfunctioning comfort-noise generator would give constant hiss, not intelligible words [3GPP TS 46.011].

Could my phone’s apps or settings trigger self-recording?

Unlikely here. The Redmi 6A lacks built-in call-recording without root. Observers watched both phones; no recording app ran [Elektroda, Anonymous, post #18191068] Malware can record, but it would not feed audio back in real time.

Will such a loop inflate roaming charges?

No. Billing starts when a call is answered and stops when either party disconnects. Loop playback happens inside the media path and does not restart call timers [Vodafone, 2021].

Can encryption failures cause cross-talk or loops?

GSM encryption (A5/x) protects each time slot independently. If clocks slip, you might hear another call briefly, but encryption errors cause noise, not coherent 50-second speech [Elektroda, Ture11, post #18192671]

How do I report the fault to my operator?

  1. Note date, time, called number, and location right after the incident.
  2. Dial your carrier’s customer-care line and request a “voice QoS ticket.”
  3. Ask for results of the trace; operators keep logs for at least 24 hours [Vodafone, 2021].

Is there an easy test for passive voice-ad targeting?

Some users talk about unsearched products, then check ad feeds [Elektroda, pawlik118, post #18191782] Ad firms deny live voice scraping; double-check mic permissions and disable assistants to minimise data collection [Google Privacy FAQ, 2022]. Edge-case: a 2020 study found 0.2 % of ads matched untyped voice topics [Northeastern Univ., 2020].

Could a longer loop happen?

Yes. Debug logs show rare cases of 120-second loops when a transcoder crashes. Vendors patch such bugs because loops longer than 90 s can trigger watchdog reboots [Ericsson PS-Note, 2019].
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