Sound ID

[DiveNav]

......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......

Very good.
Can your software run a frequency analysis? If so, can you post plot showing the spectrum with the 3 main frequencies?

 

[diversteve]

How close were you to Andros? AUTEC tests there - between Andros and Nassau/New Providence - including I believe submarine tracking. Maybe you caught one going thru...

The U.S. Navy's Atlantic Undersea Test and Evaluation Center (AUTEC) is an instrumented laboratory that performs integrated three-dimensional hydrospace/aerospace trajectory measurements covering the entire spectrum of undersea simulated warfare: calibration, classifications, detection, and destruction. Its vital mission is to assist in establishing and maintaining naval ability of the United States through testing, evaluation, and underwater research.

The sophisticated facility includes three test ranges: the Weapons Range, the Acoustic Range, and the FORACS Range, all located in the Tongue of the ocean (TOTO), a deep-ocean basin approximately 100 nautical miles (190 km) long by 15 nautical miles (28 km) wide with depths as great as 6,000 feet (1,800 m). The main AUTEC support base and downrange tracking stations are on Andros Island in the Bahamas, just west of Nassau and about 180 nautical miles (333 km) southeast of West Palm Beach, Florida.

Atlantic Undersea Test and Evaluation Center - Wikipedia, the free encyclopedia

 

[Phil_C]

Hopefully the upload will work - first time I have tried it.

The picture above shows the analysed sound signal from one set of signals. Each instance of the sound is identical -

The first sound is constant frequency at 3 kHz and lasts 500 ms. There is then a silent gap of 10 ms, followed by a second constant frequency pulse at 3.2 kHz which again lasts for 500ms. The final sound component is a constant frequency signal 60 ms later at 3.9 kHz. The sound then repeats at a repetition rate of just under a minute.

I have looked at each 'sound' instance in turn, and the signal each time is identical, same frequency, duration and inter-pulse interval. The repetition rate is around a minute between signals for the first few recordings, then changes to roughly 30 seconds between instances. After the change to 30 second repetition rate the sound characteristics still remain the same. i.e. 3, 3.2 and then 3.9 kHz and 500 ms pulses with the same inter pulse intervals. So the characteristics of the signal are unchanged except the repetition rate.

There are no echoes, harmonics or doppler shift effects visible in the signals, which suggests that they are not being received from reflections or 'bounce' from the sea bottom or water surface (in the way radio waves bounce in the atmosphere) which would suggest a straight line sound propagation perhaps from a towed buoy or submerged sender.

I have looked at some mid-frequency sonar sonograms and they show the same pattern of three (or more) cf components of similar frequency, length and duration but I have no experience or knowledge of what they are used for except that they will return distance and depth profile type information so as these are what is called active sonar, they may have been being used for sonar mapping or bottom surveys which is why they were repeated regularly, rather than a military search and locate type use.

Although I seem to remember from the old WWII films that ships turned on active sonar to "drive" submarines in particular directions when they were trying to push them into traps and so on - so someone may have been playing war-games. Any ex sailors out there can throw some light on this?

Phil.

edit - ok - jpeg not very clear - I'm happy to supply original to anyone really interested - pm me - cheers P

 

[DBF]

I am an ex submariner and have spent many hours sitting on the sonar console, this intrigues me.

Hunting subs with active sonar is a suicide mission, with modern weapons and the amount of torpedoes that can be carried by a sub would be only minutes before up to a dozen surface vessels would be sitting on the bottom

I think a computer or watch alarm can be ruled out.

With all samples being the same it appears that the source is static either a ship at anchor or a fixed source.

I cannot think of a reason that a fixed source would need to be an active system unless it was a marker but it would not need to change ping rate. An active fixed system is open to attack and upsets the marine life.

My best guess is it is a ship at anchor testing it's sonar, Doppler velocity log (used to measure speed) or depth sounder




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[Phil_C]

I

Hunting subs with active sonar is a suicide mission, with modern weapons and the amount of torpedoes that can be carried by a sub would be only minutes before up to a dozen surface vessels would be sitting on the bottom

I think a computer or watch alarm can be ruled out.


My best guess is it is a ship at anchor testing it's sonar, Doppler velocity log (used to measure speed) or depth sounder




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Hi DBF I was speaking tongue in cheek when I suggested herding subs ! - I agree completely now it is not an alarm or dive computer - the sound qualities and so on just do not support this. The timing and precision of the sounds pulses and the frequencies mean this has got to be deliberately made and propagated for some form of 'sonar' application.

I have read a little more today about the uses of mid frequency sonar and the only other thing which has come up is its use in marine topographical surveys - obviously for this purpose active v passive sonar makes no difference as you are not trying to hide or remain covert. This would make more sense with regular pulses, but at a minute and even 30 second repeat rates I wouldn't have thought you would get much survey overlap with a moving sensor. But - the complete lack of change in sound parameters from pulse to pulse would suggest the source was not moving much in relation to the divers in any event. - Phil

 

[novasquid]

this was during the bahamas bash a couple of weeks ago, and we all heard the sounds. there were variations of the sounds on different days. and it was near andros island.

the dive guide and boat captain told us it was the navy ships/submarines and possibly the sonar buoy nearby that was making the noises.

we had a great time diving in bahamas, and wish we were back there!

 

[dfx]

How close were you to Andros? AUTEC tests there - between Andros and Nassau/New Providence - including I believe submarine tracking. Maybe you caught one going thru...

At least 20 km away. On our trip to Andros, we did see a very large ship anchored there, which sure looked like a destroyer, but I didn't notice the sound on either of the two dives we did there.

this was during the bahamas bash a couple of weeks ago, and we all heard the sounds. there were variations of the sounds on different days. and it was near andros island.

Interesting, I only ever noticed this sound on a single dive and it wasn't one of the Andros dives. My video camera also captured it only on that dive, but then again I don't claim to have the most sensitive hearing

---------- Post added December 4th, 2013 at 10:18 AM ----------

While I don't have any professional audio analyzing software, I do have some basic audio manipulation skills, so I tried to isolate the sound from the background noise and amplify it. The result is this file, containing two instances of the sound: https://dl.dropboxusercontent.com/u/100480028/sonar.wav

Loaded in an audio editor, one signal then looks like this:

And here's the spectral analysis of each of the three tones:

---------- Post added December 4th, 2013 at 10:20 AM ----------

Silly forum shrank my images, here's the direct links:

https://www.dropbox.com/s/wurmzjljppbbek9/Screenshot - 120413 - 10:11:43.png

https://www.dropbox.com/s/c228k1dzuxlcd4b/Screenshot - 120413 - 10:09:32.png

https://www.dropbox.com/s/tz8iqeb19fxpd8o/Screenshot - 120413 - 10:10:33.png

https://www.dropbox.com/s/jwkekecyalecf6a/Screenshot - 120413 - 10:11:04.png

 

[iluvtheocean]

this was during the bahamas bash a couple of weeks ago, and we all heard the sounds. there were variations of the sounds on different days. and it was near andros island.

the dive guide and boat captain told us it was the navy ships/submarines and possibly the sonar buoy nearby that was making the noises.

we had a great time diving in bahamas, and wish we were back there!

so we have DBF saying with his experience with sonar saying it's a stationary object making the noises & novasquid saying that the boat captain stated there was a nearby sonar buoy. Occam's razor would say then it's most likely a navy vessel or the buoy since normal dive gear was ruled out. But of course being S.B. -- it's more fun for everyone to speculate and try to guess/figure it out. A dolphin passing gas underwater maybe?

 

[novasquid]

of course after writing about it, i can't seem to find any of these sounds on my videos. i think the other days we heard the sounds were the last two days, which you guys weren't around for. but if you remember, at andros we hung out at the sonar buoy for one of the dives and there was a navy ship in the area that day we were at the buoy.

 

[dfx]

of course after writing about it, i can't seem to find any of these sounds on my videos. i think the other days we heard the sounds were the last two days, which you guys weren't around for. but if you remember, at andros we hung out at the sonar buoy for one of the dives and there was a navy ship in the area that day we were at the buoy.

Yup, and while there were all kinds of strange sounds (mostly very low frequency) in that area, I didn't hear anything like this sound on that day. Also, this was some 20+ km away from all the other dive sites around New Providence/Nassau. Maybe one of the sonar experts here knows if this type of sonar would actually be able to travel that far and still be well audible?