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today I stumbled upon one folder in my backups I totally forgot about. It contains an audio file, a spectrogram and some observation. In mid 2017 (starting from june) my speakers began to (seemingly randomly) play 1,4 seconds of the same audio during different times. It was a 1 kHz tone. You can check the full 1,4 seconds of the audio here:

It played at different times and I could not detect any process as the source of the sound. I could capture the sound through my sound card (Asus Xonar D1) though. Does anybody know what this sound means and why it could have been played? My observations:

  • That sound was played more often between 00:00 and 02:00 UTC+2 (Germany)
  • 1410 ms duration, 1 kHz frequency
  • rise to amplitude in 9ms, comedown as well

I tried to reconstruct the durations of the sound and the silence in ascii:

Legend:

{DURATION} := Duration of the 1 kHz signal

[DURATION] := Duration of the silence

{ 209 ms } [ 58 ms ] { 74 ms } [ 58 ms ] { 74 ms A} [ 58 ms ] { 75 ms B} [ 191 ms ] { 76 ms C} [ 58 ms ] { 75 ms D} [ 191 ms ] { 209 ms }

A - additionally very weak signals appeared on an irregular basis during 7 ms

B - [...] 3 ms

C - [...] 5 ms

D - [...] 10 ms

Figure ( P = Pause (~58ms), E = One Unit of the sound (~75ms) ):

PPP E P E P E P EEE P E P EEE PPP

Message / Body maybe: E P E P E P EEE P E P EEE

Thanks in advance for everybody trying to solve the riddle.

Best regards,

sea212

  • sounds like someone transmitting morse code over radio. – audionuma Aug 5 '18 at 6:40
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This is morse code.

It translates to

BIT

  • Thanks for that solution. I wonder how whoever did this got my system to play that sound. Interesting. – sea212 Aug 6 '18 at 11:52
  • were there any more sounds or was it just BIT over and over? – Mark Aug 7 '18 at 14:12
  • It was BIT everytime – sea212 Aug 8 '18 at 15:59

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