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Old 04-05-2014, 11:21 AM   #181
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Maybe, but Chinese have been wrong a few times on their claim before. Given how things have been going, I will believe if Australians or US has more definitive evidence.
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Old 04-05-2014, 11:50 AM   #182
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This is what the ping sounds like:

What black box 'pings' really sound like – Anderson Cooper 360 - CNN.com Blogs
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Old 04-05-2014, 11:59 AM   #183
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Maybe, but Chinese have been wrong a few times on their claim before. Given how things have been going, I will believe if Australians or US has more definitive evidence.
The relationship between Malaysia and China during the ordeal is kind of ironic I think. In that China's government is known for controlling information, but in this case since most of the passengers are from China, they are the ones pressing Malaysia for truthful information.

Just ironic, IMO. Kinda like Facebook upset at being spied on.
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Old 04-05-2014, 12:25 PM   #184
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Actually, the 'ping' does not sound like anything. It is at 37.5KHz, above human hearing.

What you heard in that video was the sound of a 37.5KHz detector. The detector could be set to generate any sound at all, maybe your favorite ring-tone?

Looking back at that picture of the guy with the binoculars - doesn't the military have advanced video detection systems? We have face recognition software, I would think the military would often have the need to detect 'something' ( a person, a tank or jeep or small boat or a submarine periscope) on land or sea that stands out from the background. It doesn't seem hard to do better than a guy with binoculars.

Something that really annoys me in the reporting is when they say something like "The batteries are designed to only last 30 days". OK, They are designed to last at least 30 days. It's not semantics, those two statements mean different things. They may or may not last longer, but given that they need to design some safety factor in there, I'd pretty much expect them not to die on day 31. Now, if they've been lax in maintenance, and they are not replaced or stored as required, they may last less than 30 days.

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Old 04-05-2014, 12:40 PM   #185
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I wonder how many subs we (or the Russians, Brits, or Chinese (even the Indians have one nuclear sub)) keep patrolling in the Indian ocean? They are pretty good at "hearing" things.
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Old 04-05-2014, 03:10 PM   #186
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Actually, the 'ping' does not sound like anything. It is at 37.5KHz, above human hearing.

What you heard in that video was the sound of a 37.5KHz detector. The detector could be set to generate any sound at all, maybe your favorite ring-tone?

Yes, quite right.

I heard one aviation expert say it was 37.5 MHz.

Maybe it's a dolphin with a sick sense of humor.
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Old 04-05-2014, 04:37 PM   #187
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I wonder how many subs we (or the Russians, Brits, or Chinese (even the Indians have one nuclear sub)) keep patrolling in the Indian ocean? They are pretty good at "hearing" things.
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Yes, quite right.
I heard one aviation expert say it was 37.5 MHz.
Maybe it's a dolphin with a sick sense of humor.
When you're underwater, and within a few hundred yards of the transmitter, 37 KHz sounds like a clicking noise coming through the hull.

But oceans are noisy and all sorts of critters put out sounds at 37 Khz (and other frequencies). If there's not a lot of commercial fishing in that area of the world then the environment would be especially noisy.
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Old 04-05-2014, 04:53 PM   #188
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I recall that we had a special piece of passive sonar equipment in the control room tuned to the frequency of the active homing sonar on Soviet torpedoes (can't recall the frequency). It would beep when it heard that frequency. Any nearby dolphins would also set it off.
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Old 04-05-2014, 04:55 PM   #189
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It still doesn't make any sense to me that they didn't have recorders going the whole time. If they did, there shouldn't be much question about whether they detected anything.

I'm sure there's more to it.

This is fun:

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Old 04-05-2014, 05:34 PM   #190
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I pay very little attention to these reports.
The first one I saw talked about 37.5 KHz per second, which is kind of like saying 55 MPH per hour.

As someone else here commented a while back, the more you know about something, the less accurate the news reports seem.
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Old 04-05-2014, 06:00 PM   #191
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I pay very little attention to these reports.
The first one I saw talked about 37.5 KHz per second, which is kind of like saying 55 MPH per hour. ...
Well, it puts out a 37.5KHz burst once per second, so that's not too far off.

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Old 04-05-2014, 06:21 PM   #192
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ERD50, do you have any idea what a Hertz is?
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Old 04-05-2014, 06:44 PM   #193
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ERD50, do you have any idea what a Hertz is?
Of course. Heck, I remember when they called 'em CPS, and the inverse of an Ohm was a Mho (I always liked that one). It's also a rental car company.

I'm not saying it was 100% technically correct, I said "it's not too far off". A 37.5KHz burst once a second isn't really that far off from saying 37.5KHz once a second. They just left off the 'burst' part of it.

I need to go look this up, but I am assuming that is actually an acoustic signal so that it travels through the water. But there must also be some electrical signal, in case it crashes on land. An acoustic signal on land would not travel very far at all.

edit/add: from wiki:

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A 37.5 kHz (160.5 dB re 1 μPa) pinger can be detectable 1–2 kilometres (0.62–1.24 mi) from the surface in normal conditions and 4–5 kilometres (2.5–3.1 mi) in good conditions. A 37.5 kHz (180 dB re 1 μPa) transponder pinger can be detected 4–5 kilometres (2.5–3.1 mi) in normal conditions and 6–7 kilometres (3.7–4.3 mi) in good conditions.
So you need to be within a few miles to detect the ping. And for reference, if these were in the audio range of ~ 20~20KHz, 120db is the threshold of pain, so these things put out a very powerful tone.

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Old 04-06-2014, 10:33 AM   #194
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This ping only happens in water -- you gotta wet it to get it (see above video).

New report (cnn) says pings heard at two locations 300 km apart, so something's fishy.

Voice recorder will only have 2 hours worth -- I predict silence.

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Old 04-06-2014, 11:36 AM   #195
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So you need to be within a few miles to detect the ping. And for reference, if these were in the audio range of ~ 20~20KHz, 120db is the threshold of pain, so these things put out a very powerful tone.

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Interesting how they have detected 3 of these in the last 2 days. All the square miles involved in the search, suddenly the detect something that may be a ping. I hope it's real, but I live in Missouri, so at this point I have to say 'show me'.
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Old 04-06-2014, 01:14 PM   #196
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I would not be surprised if the Chines are putting out sucker baits for everyone.

They really want to get to the aircraft/black box first. As I am sure tha Aussies and US wants to do the same.
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Old 04-06-2014, 01:57 PM   #197
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Part of me says, "How many other things sound like 37.5 KHz bursts at intervals of one second?"

But the news isn't really giving a feeling for what's actually happening, so I'm trying to imagine how this could be a mistake.

As ERD50 pointed out, we're not talking about guys actually hearing the pulses, there's got to be a device that, as in the video above, is beeping when it detects something of the right frequency.

Also, the ship that's listening probably doesn't have specialized equipment for black box pingers. They probably cobbled something together to beep whenever something close to 37.5 KHz rises above a threshold. Not hard to do, but perhaps a little primitive.

The news shows someone holding a microphone on a pole underwater. Remember that this ship isn't the one with a towable yellow bat toy.

So these guys are sitting in the hold of a ship, watching an oscilloscope, and waiting to hear their device beep. They set the threshold lower and lower, and occasionally get beeps from background ocean noise.

At some point, they start to hear some regular beeps. Just a few in a row, and not at a frequency of one per second, but they figure they are far away, so that some of the beeps are not detected.

They play with the threshold, figuring a very low signal to noise ratio, and get a lot more beeps, but they figure that some are valid pings, and some are background noise.

This is where their imagination comes into play, transforming a semi-random series of beeps into regular beeps hiding among the noise.

I know nothing about what's going on, but that's one scenario in which people could be fooled into thinking they "heard" pings when they didn't.

Let's hope they left the 8-track recorder on the second time.
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Old 04-06-2014, 02:20 PM   #198
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...
I know nothing about what's going on, but that's one scenario in which people could be fooled into thinking they "heard" pings when they didn't.

...
Sounds plausible to me. If I were to bet money on it, and the results could be verified, I'd be looking at that as possible, and closer to 'highly probable'.

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Old 04-06-2014, 02:26 PM   #199
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This could end up the classic case of over reaction. 'We need to develop a better way to track planes' Do we? We can't find this AC because someone took action to make sure we can not find it. So not only do we have to create some system to track the AC, but the crew can't turn it off. And, we are going to develop this because we have had one incident. And, we don't even know why this one exist.
I agree. For the life of me I don't understand why someone in the cockpit is able to turn off that tracking signal.
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Old 04-06-2014, 03:05 PM   #200
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Since there have been two signals detected 300 km apart, we know that at least one of them is a false alarm.

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