Sound ID

[dfx]

Looking at this there are exactly 56 seconds between each of sounds 1 to 4 so they plot linearly - with a change then to exactly 32 seconds between sounds from that point onwards - again plotting linearly, so there is precise timing, not a random effect. The sound also appears electronically produced to me, rather than mechanical. The timing will rule out regulator noise - no-ones breathing timing is that precise.

This re-enforces my feeling that it is like some sort of watch or dive computer alarm, which when not acknowledged or cancelled changed it repetition rate from once a minute to once every 30 seconds. OK 56 seconds and 32 are not quite once a minute and once very 30 seconds but I think with the underwater effects that is what you are hearing.

In the past I have heard sounds from dive computers and wondered whose it was before realising it was actually my own, because sound does funny things underwater. The sound you are hearing is fairly high frequency, and high frequency attenuates quickly underwater (and in air), which is why whales and other marine mammals use a very low ultra sonic signals or clicks, they travel further, so I think the source of the sound was probably not very far away from you when you were recording it.

Me and my wife both have Mares Puck computers and I'm fairly certain that they can't do anything other than plain beep. Somebody else's computer or camera was my first guess too, and I was hoping somebody could identify the make or model from the sound ("oh, that's a $X $Y!"). But I guess it's not so easy

I took a second video on the same dive (I had turned the camera off in the meantime) in a different part of the reef, and while it does contain the same sound a few times, it's very faint and barely audible. However, proximity to other divers didn't seem to matter, and neither did proximity to our dive boat, especially since we were diving with the same people and the same boat all week and never heard it again. So it did seem to be something localized, but I was unable to pinpoint any particular source.

Somebody on FB suggested that it could be a locator beacon, like one used to find black boxes. That would make sense I guess, but it's still only a wild guess.

I have done a fair bit of sound analysis of the calls of birds, bats, crickets and cicadas (as an ecologist - don't ask!) and what could tell you more about the source would be running the sound through a spectrographic analysis in a software package such as Batsound from Pettersen Elektronik or Raven or Raven-Lite from Cornell University - these would allow you to see if each 'signal' was identical or whether there was some variance, other than the time intervals.

I've got both packages on my laptop so if there is some way to get the original files to me I will happily have a look.

Well, how original do you want it?

I've put the original file and some versions of the audio track here: Index of /tmp
The original file is the 500 MB MP4 video file: http://dfx.at/tmp/FILE1201.MP4
Its audio track is in AAC format. I could dump the raw audio track into a file and make it available, but that creates a file without any headers, which makes it highly unlikely that any software can open it. I know I can't.
But I could dump the audio track into a PCM WAV file. It comes out as a 150 MB file in 32-bit floating point PCM format: http://dfx.at/tmp/32-bit.wav
Since this is a bit of a silly format, I've converted to more conventional 16-bit PCM at 70 MB: http://dfx.at/tmp/16-bit.wav
Which then can be compressed down to 30 MB using FLAC: http://dfx.at/tmp/16-bit.flac

Can't say that you don't have choices

 

[Phil_C]

Hi DFX - thanks for the links - a 70 mb wav is no problem for the analysis software so I will download that and have a play around with it and see what it looks like. I'll post the results back when I get a chance. I'm sat in a hotel in the middle east so hopefully the wireless will be up to the task but don't reckon the 500 mb will download that well here.

It probably won't be until tomorrow (it's very late here now) - before I get a few minutes to look at it but I'll post back when I have done it. Cheers - P

 

[LivingTheDreamBaby]

Just a bit more incite on this. There were 14 of us in the water, spread out over several hundred feet and yet we all heard these sounds as clearly as if they were from our own computers alarming. The best explanation so far, seems top be sonar from a USN Submarine operating off the shelf, but I'm sure we're all looking for positive confirmation on this. Any additional help would be appreciated. Obviously we need to rule out computers, reg's, dive boats, etc......

 

[Phil_C]

OK - it didn't take me as long as I thought and was not what I was expecting -

The sound components are electronic, all exactly 500 m/s long and regular constant frequency (c/f) sounds - cf is virtually unheard of in nature, but some bat echolocation is cf in the 70-110 kHz range.

The sounds in the recording are all cf in the 3 to 4 kHz range, so I ran the parameters against known maritime noises and noise pollutants and came up with a match -

The signals have all the characteristics of C53 mid-frequency military sonar - in 2003 active C53 sonar used by the USS Shoup in the Washington Haro straights led to recorded distress in dolphins and cetacea and complaints to the Navy from the National Resources Defence Council.

So I will eat my words about dive computers and join the big brother conspiracy theorists !

I found a sound sample of C53 active mid frequency sonar - Mid-Frequency Sonar | Ocean Conservation Research

Click the link button on the right and you will hear a sample. The only discernible differences between the signals are that the recording from dvx doesn't have a terminal 'click' for each pulse set, and the signals from dvx do not have harmonics, it is a much cleaner and more focussed, clear signal - perhaps a development and improvement over the original or just better recording conditions..

Now I better get to bed - :dozingoff: - Phil.

 

[dfx]

Well that sure does sound a lot like it! Not a perfect match, but much closer than all the silly sonar "ping" sound that I found lol

 

[Phil_C]

Another C53 mid frequency sonar sample here - but there don't seem to be many recordings around - I wonder why

Dreamtoby.de | Podcast

P

 

[letterboy]

Great, now so is going to be shutdown while the dod this "spill"...

 

[tursiops]

Great, now so is going to be shutdown while the dod this "spill"...

Can you repost this in English?

 

[letterboy]

So = SB

Dod cleans= department of defense cleans ..

Any other errors?

That's what I get for posting from a red light..

 

[DBF]

Very unlikely to be a submarine, as if they go active ping at all they generally only do one or two pings to signal a location or confirm a target and then go passive again. it the nature of a sub to be as quite as it can be


The change of rate between pings may indicate a change in range setting on the device in question.


Phil could you see any slight difference in frequency between the first and last ping. If the time duration between pings was large enough and there was a frequency shift then it may be a moving vessel searching for something ie warship playing war games, they typically don't sit still and active ping as this makes the a very easy target and a change in frequency could be due to the doppler effect.


Also the doppler effect could be masking the original frequency and may not have been generated in the 3-4 khz range it may have traveled a long distance because a sonar ping is designed to travel more than twice the detection range.


It is unlikely to have been a fishing boat you could not see as the generally don't have the output power on their fish finders/depth sounders to have a ping travel long distances they don't normally require them and it is an unnecessary expense.