How detect if MP3 player is recording in your room? [OT]

semiconductor

Yep, and that can be detected. What you do with the knowledge that the person has an electronic device that may or may not record is up to you and what you want to do.

By that you must specifically mean the cell phone. Clear details matter a lot.

It's essentially useless information because in modern societies every other person has a cell phone or beeper, MP3 player or whatever. One could not conduct business in an environment where they had to make some random speculation every time they came across the existence of an unknown electronic device, but as importantly, it still has not even been established than in any specific scenario, the MP3 recorder would be detected at all. yes it's possible to detect that an object exists, but it's also possible to have a scenario where the testing method doesn't detect it.

Yep, that is all you have. Another such technology is called Quadrapole Resonance or QR. Originally developed by the Department of Defense to detect land mines, QR directs a beam of radio waves at an object. The radio waves will penetrate the object and infuse whatever is inside. When the radio waves pass through an explosive material, the molecules of that material will polarize or develop a small electrical charge. As the molecules lose their charge, they emit a very weak radio frequency signal that can be picked up and analyzed to detect explosives. Because it relies on harmless radio waves that are easy to produce and monitor, this technology is considered to be one of the most promising in the field.

And another one that needs to keep up on technology Here are some links that will explain what I am talking about.

The phenomenon of nuclear quadrupole resonance is akin to nuclear magnetic resonance, which is the basis of magnetic-resonance imaging. But unlike MRI scanners, instruments based on nuclear quadrupole resonance are not required to generate strong magnetic fields.

down

Enough

No, by that I mean any electronic device, which may or may not be used to record conversations.

that

Nope, it will tell you that the person has an electronic device that may or may not be used to record your conversation or take pictures. This is where security comes in, and how much security you want to enforce.

All this proves is that you have not read or understood my earlier posts. I described the way actual devices operate to detect any device that is detecting audio. It shouldn't be hard to realize that any device that is responding to a pattern of sound is a threat. For a recorder, of any kind, to record the audio in a room it must detect it, and amplify the detected signal. These processes can be detected, if this processing matches the on and off timing of a known pattern of sound, (which you control) you can isolate the device. (Your "2" above.)

I hope you aren't going to say that while this type of detector can detect that there is a device responding to the sound in the room, and help you locate it; this hasn't identified the device as an MP3 recorder. I would think even you realize that it is of no importance what the device is, that is responding to the audio pattern, it would need to be considered a live threat.

You might check into why the most expensive "White Noise Generators" include a means to inject a user supplied signal into them.

Luck; Ken

Detecting and locating any device intentionally transmitting an RF signal is trivial in relation to this discussion. But the kind of device I have described can certainly detect that it is responding to the audio pattern, and locate it.

Luck; Ken

You made a suggestion that was not resolvable to a difference in operation of an MP3 player. With a constant current and constant bitrate output, you'd essentially be suggesting that from a distance you can discriminate which bits are flowing on the bus to the memory, in what is likely a shielded case. I find this highly unlikely.

Sure, but even ignoring the issue of whether it's feasible to have test sound patterns at all, we don't have any evidence a digitally recording MP3 player will have a detectable response in particular scenarios, if in any at all.

The recorder does not necessarily need amplification prior to digitization, it is commonly a single chip solution that would not have to output to headphones either in this use.

"IF" the process existed, and "IF" the detection device was suitable sensitive, and "IF" the scenario allowed proximity, then perhaps it's possible. None of these three IFs can be assumed yet.

Not at all, I'm going to say the device won't detect the MP3 player recording at all in most scenarios, that it might detect "something" electronic is in the room but that's all, it won't ID it as an MP3 player nor that it is responding to sound in the room. "Maybe" if you had it right up against the recorder, but do you expect that scenario?

You're drifting down a tangent that has not yet been reached. I never argued that a detected response to an audio pattern wasn't suspicious enough to draw a conclusion about the operation of a device.

It still doesn't get us where we need to be, to detect a recording MP3 player reliably and discriminate it from other non-recording electronic devices. This is not the same as a tape recorder.

I was suggesting no such thing. I find your idea that an ungrounded MP3 recorder has any significant shielding, very unlikely. The recorder to be a threat and to respond to sound must let sound waves through, even if it is a contact microphone/sensor/transducer, and they require significant amplification in their operation.

It is not necessary to know "which bits are flowing on the bus to the memory", the detection takes place before that is even an issue.

If you are going to pretend you understand how the device I described operates, try to approach it from a different angle than; finding a way it couldn't work, then deciding that is what I must be describing.

So now you doubt that it's possible to generate a controlled pattern of sound? (You wouldn't be responsible for Rap "Music", would you?)

I'm no giving you "evidence". But I must have missed your "evidence" that the device I described doesn't work. Evidence is something besides your opinion, or your interpretation of High School Physics and needs to be based in proven limitations.

Try the following:

Almost all audio detectors/sensors require amplification, and those that don't, carry a significant bias current that gets modulated, more than enough to be detectable with modern equipment.

Isn't it fortunate that no one needs your agreement that it's possible, to make and use such devices.

I say that such devices can detect any device that is responding to a supplied audio signal pattern. Any device that is detecting the audio pattern. They can detect anything electronic, that generates electrical noise or signal when it detects acoustical energy.

There is a great deal more some of these devices can do in the hands of a skilled operator/analyst.

It looks like we have established that you are going to just deny the possibility. You can believe what you wish, it has no impact on reality what so ever.

You have been provided a description of how these devices can do just that, your only answer seems to be that you don't believe a device could work as I described. You provide no explanation (much less evidence) of why it couldn't work.

You seem intent on saying "No they can't work." I know that they most certainly do work. What point is there in further argument, on that basis?

Luck; Ken

That signature ... would it be from the azide bonds in a heavy metal azide, from the nitrate bonds in RDX or PETN cubane nitrate, or from the nitrate bonds in the current scare-of-the-month acetone derivatives? It would be a breath of fresh air if it were. (If your chemistry isn't good enough to spot the trap in this question, be very, very careful.)

More to the point, since someone was talking about an office-like setting, would be things like SCR (triode) dimmer switches built into the walls of the room, for perfectly good reasons. The phrase is "false positive", and if anything they're even more corrosive of ones confidence in the usability of a detection system than are false negatives. (Had a bad week last week with a poison gas detector system going off every couple of hours. Every false positive meant that I had to kit up with the breathing apparatus and go to check the situation out.)

Define significant. Many have grounded copper foil in them. It's not as though this is a high powered device to begin with, though, and would commonly have to be detected at a distance.

No, you are thinking of older devices. There needs be no amplification prior to the digitization chip which can run at constant current, very low voltage and no easily detectable response to room noise from a distance.

We might consider it mere coincidence that it is recording something, because the means to that end are different than in a recording device with a different (end) medium and analog amplification.

You mean "IF" it could, it would.

I'm not going to pretend anything, I'm suggesting you are not describing an MP3 player in recording mode.

All the rest of your supportive argument hinges on being able to detect a signal that may not exist at all, or in cases where it does, are not sufficient strenth to measure at any distance. Remember it is not enough to find one particular MP3 player, nor a dissimilar device like a tape recorder, that can be detected- it has to be effective against the entire class of devices, or at the very least the common ones available on the market.

Still consumer electronics do not have very good shielding. Hence it would be a very minor task to detect the sampling clock of the recorder in question. And most of the times the sampling rate is specified by the MFG.

You still have the sampling rate, which requires a clock at that rate, so at a minimum that clock can be detected. And most designs would include an amplification stage prior to digitization, as the levels from most mics will not be sufficient, and also to add isolation between the input stages.

Doesn't have to be *very good*, only has to further reduce emissions which likely weren't at a level high enough to discriminate recording mode even without the shield.

That does not indicate it is an MP3 player, let alone recording. There is no one "sample clock" common to all MP3 players.

Manufacturer of the chip, yes, not the MP3 player, and "spec" really means, hardware support as it can't be selected at random like with most computers running soft codecs. Even so, this rate is not usually a separate oscillator, the chip itself has a clock that can also vary per chip. It is certianly not something that remains constant over all MP3 players, and not a signal that appears only when set to recording mode.

No, it does not. Clock rates are divisible or multiplied these days, and these rates are often common to process sizes, or current targets, not a specific functional requirement. In other words, it's a safe bet you cannot detect a recording MP3 player with a universal "sampling rate" detection scheme, even before considering they won't all necessaril record at the same rate, further lacking consideration for any possiblity of variable rate or spread spectrum.

Sufficient for hearing through earbuds, no, that'd be amp'd.

Sufficient for a microchip DESIGNED to use a mic input to digitize MP3? It would be an incredibly poorly designed chip if it had to have a preamp tacked on after the mic.

You are thinking old-school multi-stage, possibly even discrete audio designs. All-integrated single chip MP3 players (recording) isn't directly applicable.

And most consumer electronics are not very well shielded, hence it is a snap to pick up their emissions with off the shelf test equipment.

So what. It still indicates the presence of a device that can record the persons converstaion, and that is what is required. It can be a dictation device some other kind of recorder, it would still be detected.

All you need is the chip, and usually the OEM will list what the chip MFG states anyway.

Usually you have an external clock needed to feed the codec. That clock can be detected as well.

Without a sampling rate, there will be no conversion of analog to digital. You have to take so many samples of the analog signal.

digitization,

"Most" don't have any shield at all. MP3 players, commonly do. Further, "most" consumer devices have an order or two of magnitude, more active parts in them and use far more power, stronger emissions.

Further, detecting a very faint signal is not the same thing as having a strong enough detection and valid discrimination method between recording MP3 players and all other consumer electronics. Remember that we are not just trying to detect that some "thing" using electricity is present, it has to be identifed in function and is not just one device buy a multitude of different MP3 player (or other digital recorders too if you want to consider all types) recorders.

You will have to find a specific commonality, not just a vague generalization, to discriminate them. Even this much is premature- that commonality would have to exist which has not in itself been established.

No it does not. Did you think nothing but MP3 players have clocks, or that all MP3 players have the same clock rate? Neither is true.

No, in some cases you might detect some devices, but it'd be random, you'd far more often detect non-recording or devices completely incapable of recording and wouldn't detect some actually recording. In other words, random and useless.

You'll need ALL of the chips in existence, and you'd find some are not putting out enough noise to be detected in a typical scenario. Maybe if you put a scanner up against the device. Is that really useful? If you had the device out already, no further scanning is needed at all unless you have far-fetched idea like if the MP3 recorder were built into a shoe-heel or a clock, etc. Even then, it's a matter of scenario. If that scenario doesn't allow getting the scanner close enough to find the shoe is a source, you'll never even know it was suspicious there was a noisey shoe.

I've gone off on a tangent though, for our purposes an MP3 player should be considered what is bought off the shelf. OEMs do not "list what the chip MFG states". Most often you have to tear open the specific player and examine it yourself, or rely on reports from someone else who has.

Again you are thinking of older electronics, today's player/recorders are highly integrated. That doesn't mean ALL devices will have a different or undetectable, or indistinuishable clock signal, but it does mean you don't have a commonality that allows detection as an MP3 player, let alone one recording.

The existence of a sampling rate does not suggest it is always the same rate nor that it is measureable in any particular scenario.

Yes, but this does not lead to any of the other conclusions.

It all boils down to a weapon vs armor arms race.

Suppose one vendor produced a device that can detect some device which samples at 8 kHz. More likely it will detect frequencies that are multiple of 8 KHz. Then, an MP3 recorder doesn't have to use any external xtal frequency which is n*8000 - an on-chip PLL is commonplace. A mic is connected directly to the chip, so it won't give any EMI.

Most reliable signature would be periodic access to the flash serial interface, though.

Still, if someone wants to record a conversation, undetected, a custom shield may be manufactured for the recorder (like 1 mm of permalloy/copper sandwich), and bingo: no detection.

Right it's a secret part of an "arms race", but the same lab(s) are developing surveillance equipment and counter- surveillance equipment. With unlimited funding, you can have your "Undetectable Device" and you can have a Device to detect the undetectable. It becomes what you can have at what cost and in what numbers. The more expensive and rare devices are reserved for the most sensitive and vital situations.

It is in the interest of those working the counter-surveillance side, that those thinking of using a surveillance device, not know the likelihood of their being an effective detection device in play or not. Things electronic get cheaper all the time, last year's rare laboratory sensor may well be in next year's field unit.

Luck; Ken

Don't forget the full cavity search before and after. 8)

With the size these things are getting today, some Xt-ray imaging will also be necessary....

Arno