Acoustical Attacks against Hard Drives

Interesting destructive attack: "Acoustic Denial of Service Attacks on HDDs":

Abstract: Among storage components, hard disk drives (HDDs) have become the most commonly-used type of non-volatile storage due to their recent technological advances, including, enhanced energy efficacy and significantly-improved areal density. Such advances in HDDs have made them an inevitable part of numerous computing systems, including, personal computers, closed-circuit television (CCTV) systems, medical bedside monitors, and automated teller machines (ATMs). Despite the widespread use of HDDs and their critical role in real-world systems, there exist only a few research studies on the security of HDDs. In particular, prior research studies have discussed how HDDs can potentially leak critical private information through acoustic or electromagnetic emanations. Borrowing theoretical principles from acoustics and mechanics, we propose a novel denial-of-service (DoS) attack against HDDs that exploits a physical phenomenon, known as acoustic resonance. We perform a comprehensive examination of physical characteristics of several HDDs and create acoustic signals that cause significant vibrations in HDDs internal components. We demonstrate that such vibrations can negatively influence the performance of HDDs embedded in real-world systems. We show the feasibility of the proposed attack in two real-world case studies, namely, personal computers and CCTVs.

Posted on December 26, 2017 at 9:34 AM • 57 Comments

Comments

ARLDecember 26, 2017 10:17 AM

The Youtube video linked in this comment's URL field is almost 9 years old, but it provides a demonstration of much lower-tech acoustical attack on hard drives.

WaelDecember 26, 2017 10:56 AM

Funny we were talking about trips in a different thread. What I'd like to have is one of these bad boys. Magnetic attacks against hard drives are more interesting :)

Go on a Monster Magnet trip.

markDecember 26, 2017 12:01 PM

Interesting... but exactly how practical is it in an organizational environment, where you have locked server room, and many servers?

For that matter, how do you deal with one system with multiple hard drives from different manufacturers, of different sizes? I'd suspect they all had different frequencies.

Old school December 26, 2017 12:20 PM

April fools! It was just an infected .pdf to test your tendency to click things.

Welcome to the Schneier botnet!

neillDecember 26, 2017 1:00 PM

@wael

years ago i experimented with magnets extracted from defective HDDs placed ontop an older working, running drive

depending on the placement i got either many read errors, frantic clicking sounds, but in some cases it actually sped up random access times by a few ms.

guess placed just right the actuator can reach its intended position quicker with a higher field strength.

RachelDecember 26, 2017 1:14 PM

Kudos to Clive.

Not read paper but may be implications for retrieving encrypted data at rest. what about SSD?

I recall either Nick P or Dirk Praet stating they knew someone whom fired a gun at a HDD and data survived. ridiculously resilient, really. Anyone here still use 7inch or 3.5inch floppies?

DeborahDecember 26, 2017 1:22 PM

I can't help but be reminded of Hofstadter's "music to break phonographs by" in Contracrostipunctus (from Gödel, Escher, Bach, of course)!

Clive RobinsonDecember 26, 2017 1:42 PM

@ Mark,

how practical is it in an organizational environment, where you have locked server room, and many servers?

It rather depends on how your sound generating transducer works.

In a moving coil speaker you have a large surface driven by a coil the moves in sympathy to the energy in the coil at any given moment.

So... Find a metal plate and hit it with energy in the right way and it to will vibrate in sympathy with the energy involved.

You may or may not know but those high power laser weapons the military develop actually often work by sending pulses of energy that cause the target to destructively resonate...

So if the computer you wish to attack is visable through a window something like a half kilowatt CO2 laser may well go through the glass and if pulsed onto the case of the computer may well produce the desired acoustic wave to cause resonence in the hard drive.

@ All,

You might not be aware but the platters in hard drives have become so thin that light weight metals are not suitable. As was famously said about this a decade ago "If you keep thining out aluminum whay do you get? Baco foil". That is you get to the point where the materials plastic limit is easily crossed so any minor bend ends up permanently distorting in. Glass however is somewhat different you can thin it a long long way without getting to it's plastic limit. Thus strangly glass is a way better material to make platters out of.

However... Most of us have probably seen a video of a wine glass being shattered by sound from a nearby speaker played through an annulus or similar. If lucky you will see the video of the wine glass slowed down 10,000 times and see it flexing and bending in sympathy to the sound wave.

The point is that a glass plater will likewise flex, but it does not need to break, it just needs to be enough to move the magnetic domains for each data symbol[1] far enough for it to appear corrupted.

[1] Modern hard drives do not store individual bits but symbols made of multiple bits with redundancy / error detection correction. As with the improvements from helium-filled drives, Shingled Magnetic Recording (SMR) technology allows for higher capacity on hard drives than old traditional storage methods (MFM RLL) it works in a similar way to ISI tranmission systems by interleaving data tracks like the shingles on a roof thus data density 25% or more than other techniques.

CallMeLateForSupperDecember 26, 2017 2:46 PM

"Anyone here still use 7inch or 3.5inch floppies?"

Me do. :-) 3.5's, in 720k and 1.4M. Hundreds of them. Still use them, but on the OS/2 Warp 'puter only. Have not figured out how to make Linux give me access to the floppy drive.

I still have a box of 2.8M 3.5", used for backup on Thinkpad 720C eons ago, but that puppy died in the aughts.

I think I have some 8-inch ... somewhere. Boot floppies for IBM 4341.

MikeDecember 26, 2017 2:47 PM

Deborah, you beat me to it. I was about to say the same.

As you recall, Turtle made a record with sounds that wrecked Crab's record player using acoustic resonance. Interesting to me was what followed. Crab installed a scanner to check for player-destroying music -- so Turtle made a record that used the same method to destroy itself. When that was blocked too, he made one that destroyed the scanner.

Finally, Crab made a player that would only play his own records and reject unrecognized ones. Turtle then made ones with spoofed labels to sneak in.

It sounds a lot like the security arms race we deal with.

albertDecember 26, 2017 2:53 PM

@Wael,
The magnet on server video was interesting. Having that sort of access, one would think a hammer would be faster and more efficient. :) I see the value of a remote DOS attack if you want it to appear as a 'normal' disk failure, but the tech isn't there yet.

Note: Despite their precautions and technique, the guys should be wearing leather gloves and industrial eye protection, if, for no other reason, than to show a good example to idiots who might try the same thing.
..
@Clive,
How exactly does an IR laser cause resonance effects?
I would view microwaves as the medium of choice for server attacks. I haven't seen any server rooms with windows or outside walls, but modern ones have concrete floors and metal walls.
..

Access through the Internet is still the best way to go, and it seems fairly simple in comparison to acoustic methods:)

Does anyone have info on the microwave sensitivity of computers?
. .. . .. --- ....

RachelDecember 26, 2017 3:20 PM

Deborah
Mike

Beautiful! !!!
This is a mission for highly influential Nick Cage
(all kinds of innovations with sound and music. His machine for creating the longest note in history is in the Smithsonian)

AnuraDecember 26, 2017 5:40 PM

Personally, I don't see why you wouldn't just use an electromagnet. Much safer to handle and not nearly as expensive.

Clive RobinsonDecember 26, 2017 5:42 PM

@ Albert,

How exactly does an IR laser cause resonance effects?

In the same way a gong player does with one of those eight to twelve foot diameter gongs, or a Class C/D/F RF amplifier.

You use the laser to hit an "energy storage" component such that some of the energy gets stored. Kind of like you flicking the edge of a wine glass. The energy stotage component has a "Quality" or Q factor that if perfect none of the energy would disipate unless "quenched" or coupled out. As a general rule of thumb, high Q components when of opposit types tend to have narrow bandwidth resonance.

So if the laser hits a flat surface the heating effect will cause a shock wave to spread in the surface and reflect back from the edges or other discontinuances. If you time the second and subsiquent pulses the surface will just like the cone of a speaker couple the energy onwards into the air as a sound wave. Obviously the less round the surface is and the further from the center the laser hits the greater the "multipath" effect causing not just waveform cancelation at different frequences but many resonant frequences (which also if the surface has nonlinear response can give rise to frequency multiplication and even parametric amplification).

So each pulse of the laser will behave like "an energy pump" which if timed correctly will cause inphase energy addition. Gong and symbol players have been aware of this for centries and can build immense amounts of energy in them which can then be released as bursts of powerfull sound waves or as very long sustained sound output.

The trick is to get efficient energy coupling from the laser into the flat surface, and then into the medium (air) inside the enclosure of the computer at the right frequency to cause it to then be coupled into the device under attack normally at one or more of it's self resonant frequencies, thus building up energy in the device possibly causing it to break.

As I've indicated before any radiated energy source can do these sort of tricks. One such is to use a 10GHz/3cm EM source that will easily get through ventilation slots in cases (they act like slot radiators in reverse coupling energy back into a case).

This EM signal can be modulated at a lower frequency that due to nonlinear behaviour at any semiconductor junction will cause the "envelope energy" of the EM signal to be coupled into the wiring etc in the case. This lower frequency can it's self be modulated such that it in effect causes digital signal levels to change thus inducing faults in circuits.

The possabilities are such that sometimes I wounder why the heck anything works in the first place ;-)

Clive RobinsonDecember 26, 2017 6:15 PM

@ Albert,

Oh one thing I did forget to mention, is that many people who have never tried coupling energy in such ways will claim it's either not possible, or only possible in theory (we see this almost as regularly as the sun crossing the horizon).

Untill.... Some under grad goes out and takes half a day to knock up a rough proof of concept and another week to make it solid and write a paper on it... I've lost count on the number of times it's happened on this blog. If you want an example search for BadBIOS...

The thing is I did these experiments back in the 1980's and nobody wanted to know back then. Now however thirty years later when it's dead easy to do people still want to keep their heads down in the sand and deny it, then when some young upstart demo's it... Then the lifted heads claim they knew all along or some such tosh.

There is only one touchstone you should use with these ideas and that is,

    Do the laws of physics alow it?

And if the answer is yes you can be sure that someone will try to exploit it as BadBIOS fairly quickly proved...

This is especially true of the likes of the SigInt Agencies. Even if an idea looks virtually impossible, they will test it actually is impossible... To see what the limits of "possible" are, to either exploit them or protect against them.

This kind of stems from a more obvious idea from the SigInt agencies, as a rule of thumb they do not field crypto methods they do not know how to break and have in fact done so. After all how do you test somethings real strength? Only by breaking it...

So expect all the old deniers untill some under grad in a UK or Israeli Uni has read this and pushed out a paper in a couple of weeks...

JackDecember 26, 2017 8:11 PM

Another devastating negative performance influence attack is to hit the hard drive with a fire hose.

Grant money please.

HermanDecember 26, 2017 11:17 PM

I think hitting something with a hammer could also be considered an acoustic attack and it works against anything.

If at first it doesn't work, just get a bigger hammer.

Clive RobinsonDecember 27, 2017 3:13 AM

@ Herman,

If at first it doesn't work, just get a bigger hammer.

Hmmm or as Archimedes said,

    Give me a lever and a firm place to stand and I will move the earth.
[1].

Theory is fine, it's the darn practicalities that get in the way... It's why man's mind made CGI ;-)

[1] There are so many versions of this quote poor old Archimedes must have spent a lot of time saying it... Either a skeptical lot them ancients, or experimental physicists just conecting one of them theoretical types to the real world ;-)

Clive RobinsonDecember 27, 2017 3:57 AM

@ Rachel,

This is a mission for highly influential Nick Cage

Whilst Nick Cage has been influential in the world of film, are you perhaps thinking of John Cage who was responsible for musical works such as "4 33" and "As Slow as Possible"?

His latter work is currently being played in a Church on an organ and if everything goes to plan should take around 6/8ths of a millennium to finish... So no hurry if you want to drop in and listen, apparently the next cord change is in 2020.

https://en.m.wikipedia.org/wiki/As_Slow_as_Possible

Clive RobinsonDecember 27, 2017 4:15 AM

@ CallMeLate...

Have not figured out how to make Linux give me access to the floppy drive.

There are some versions that have drivers that still work with older hardware. I still have a 486DX box with Slackware that works reasonably well for what it is supposed to do. Have a look in second hand book shops you sometimes get lucky with early Linux books that still have CDROMS/DVDs in them and early Linux, which works supprisingly well.

As for more uptodate I did look at Puppy Linux some years ago it still supported the older hardware back then, I don't know if it still does. But there are bound to be some,"Linux lite for old hardware" distros still around.

But for my sins I have a copy of Consensys AT&T SysV4 on just under a hundred floppy disks. It kind of pre-dates Linux... Oh and I've also SCO on floppies as well, that was eye wateringly expensive when I got it. It cost the equivalent of six months take home for an engineer...

And attentive readers will know I still use an Amstrad CPC640 "lugable" with dual 720K drives, and an Apple ][ with 180K single sided 5.25 inch drives.

SpellucciDecember 27, 2017 5:12 AM

@Clive "The possabilities are such that sometimes I wounder why the heck anything works in the first place ;-)"

We computer programmers rarely see our software actually working. It is always in pieces on the floor while we assemble and test it. As soon as it works, we break it again to add the next feature.

I am constantly amazed when I go into a store, buy a pair of socks, and they work the first time I put them on.

Petre PeterDecember 27, 2017 9:54 AM

It will make me think of Van Eck phreaking on LCD when it will be proved that solid states are also vulnerable.

CallMeLateForSupperDecember 27, 2017 10:47 AM

@Spellucci
"We computer programmers rarely see our software actually working.[...] As soon as it works, we break it again to add the next feature."

My condolences. Really. Although I was never invested in "that side of the house", I worked side-by-side with it and witnessed the pain. (Pain that I inflicted by beating their code "about the head and fin" with my s/w test tools, to failure)

I always considered the assurance role more interesting and fulfilling and also much less stressful than the development role. While "they" sweat bullets to get their hardware and firmware "pretty much working" on what was always a too-short schedule, I studied their new spec docs and leisurely tweaked my existing test tools appropriately (and wrote a new s/w tool when necessary). When their stuff was finally "thrown over our wall", we were ready to attack it. Having possessed an engineer's brain since childhood and ultimately becoming a professional EE, I loved to make stuff. But I best loved breaking stuff (at first with a suitably heavy object, later with "legal" hardware/software tools.

Testing a thing affords the opportunity to see the extent to which we are as smart as we thought we were when we designed the thing.


"I am constantly amazed when I go into a store, buy a pair of socks, and they work the first time I put them on."

I know what you mean. Occasionally stepping back and looking - really *looking* - at a thing or its function can spur new insight. Upon wearing out a replacement for the replacement for a manual can opener that I had purchased in 1972 (yes, three of the suckers), I dug into my box of Never-Throw-Away stuff and retrieved a big pill bottle containing several P-38 can openers. That was in in the 1990's; I am still using the same P-38.
https://en.wikipedia.org/wiki/P-38_can_opener
(Above article states, "The can opener is pocket-sized...". That's a big understatement. Notice the hole in one end. It was common to string the P-38 on the bead chain with one's dog tags.)

CallMeLateForSupperDecember 27, 2017 11:22 AM

@Clive re floppy drives on Linux

Thank-you for making time to address this issue.

I posted queries on the official Ubuntu forum a couple of times. I got answers, none of which was "Floppies don't work on Ubunto", and I got some authoritative-sounding suggestions for making configuration changes via command-line, none of which did a whit to eliminate the problem.

System interrogated floppy drive at boot time and did recognize it as a FDD, but always threw up when trying to read or write a diskette. If I merely swapped a bootable DOS or OS/2 HDD for the Linux HDD and re-booted, the same FDD and diskette - on the same system, mind you - worked flawlessly. By the way, the mobo was a mid-aughts Asus w/ 3GHz Pentium D, so contemporary with the Linux I was using.

A friend asked me why I didn't just buy a USB FDD. Uh... wha'... USB? I didn't know there was such a thing!! But never mind.... I concluded in the mean time that I could not justify using floppies with Linux.

cDecember 27, 2017 12:25 PM

@Clive
"So if the computer you wish to attack is visable through a window something like a half kilowatt CO2 laser may well go through the glass and if pulsed onto the case of the computer may well produce the desired acoustic wave to cause resonence in the hard drive."

if by "go through the glass" you mean "break the glass" then yes, it will. Glass does not transmit well in the infrared (meaning here not near-IR, but 10.6 micrometer CO2 laser wavelength). But then, why not just throw rocks at the computer visible through the glass?

There are lasers that will do it, of course.

JackDecember 27, 2017 1:36 PM

"I concluded in the mean time that I could not justify using floppies with Linux."

Turn in your beard.

CallMeLateForSupperDecember 27, 2017 2:36 PM

@Jack
"Turn in your beard."

Never! Friends of 40 years would not recognize me. Besides, I'm quite attached to it.
Military service turned me against killing, queuing, uniform attire, haircuts, and shaving.

justina colmenaDecember 27, 2017 4:16 PM

... prior research studies have discussed how HDDs can potentially leak critical private information through acoustic or electromagnetic emanations. ...

The bandwidth of information leaked by acoustic vibrations cannot exceed the audio frequency spectrum of the vibrations, by Claude Shannon's Fundamental Theorem of Information Theory.

This may be fairly easily mitigated simply by encrypting hard disk drive storage.

we propose a novel denial-of-service (DoS) attack against HDDs that exploits a physical phenomenon, known as acoustic resonance.

Nothing new under the sun. Excessive vibration or acoustic resonance can cause any physical device to fail catastrophically.

https://www.wsdot.wa.gov/TNBhistory/Machine/machine3.htm

Encryption could possibly also mitigate this problem by replacing any "data resonance" with uncorrelated (or difficult-to-correlate) white noise. Likewise, an army never marches in lock-step across a bridge. They have to break it up and take nice easy strides, each man independently, when they are on the march and must cross a bridge.

Clive RobinsonDecember 27, 2017 11:04 PM

@ Petre Peter,

It will make me think of Van Eck phreaking on LCD when it will be proved that solid states are also vulnerable.

Already done well over a decade ago,

https://www.lightbluetouchpaper.org/2006/03/09/video-eavesdropping-demo-at-cebit-2006/

The price of FPGA / SDR boards to redo the above work are now well within "Pocket Money" range of many amateur radio enthusiasts. But likewise the performance of PC's has gone up several orders of magnitude in the same period as have various SDR devices.

You can see a sample of what's available at,

https://uk.passion-radio.com/gb/sdr-equipement/22

Have a look for the SDR devices with a 50MHz bandwidth interface.

They also have the Log Periodic Antennas in 850-6,000MHz range, as well as pre-amplifiers and suitable low loss leads etc.

Any SDR receiver or transverter which advertises that it works with GNU Radio will alow you fairly easy access to the knowledge and algorithms to stich a high performance Wim van Eck Video surveillance device up.

Further if you have a "Person of Interest" type scenario you will find information on the NSA TAO Group "video cable" devices from the same time period. Similar if not improved cables etc are now manufactured in quantity in places like China... That will give you a vastly increased range...

All of which makes a deep hole in the ground sound rather desirable if you have anything on IT equipment you realy realy want to keep private...

RachelDecember 28, 2017 7:22 AM

Clive

Hello. there.
I must thank you again for your various sharings on SDR on this site.
Has your son ventured into SDR as he quests for the satellite realm?
I'd would wish for Mr Schneier to comment / post upon upon SDR as per the security sphere. Its undoubtedly a rich and bottomless vein to tap
I recall .Figureitout has a thing for it.

albertDecember 28, 2017 12:46 PM

@To Whomever It Applies,

Thanks for the info on IR resonance. I still think microwaves are the way to go. BTW, HVAC systems can provide channels(wave guides?) to the server, without leaving the roof:) Many years age former colleague had done maintenance work at a high security gov't bldg. He was accompanied by an agent for the day, including restroom breaks.

Actually, one could 'modulate' the carrier at audio (that is, at resonant frequencies) for that desired effect, but frying the circuitry might be vastly more effective. It depends. Making it look like a 'normal' failure might be desirable.
..
If your system has floppy drive installed, and you run Linux, look up udisks. I have such a system. I 'manually' mount and unmount the disks (actually, short scripts do it). All I needed to do was copy the data from the disks. There are also USB floppy drives. I wouldn't recommend regular floppy use; why bother? Archive your old floppy data.
..
John Cages premier of 4'33'' was 'performed' in a small theater, where the backstage area could be opened to the wooded area behind the building. Thus in addition to the audience ambiance, nature contributed its own background. There are innumerable possibilities for future performances.

"...They missed the point. There's no such thing as silence. What they thought was silence, because they didn’t know how to listen, was full of accidental sounds. You could hear the wind stirring outside during the first movement. During the second, raindrops began pattering the roof, and during the third the people themselves made all kinds of interesting sounds as they talked or walked out.
— John Cage speaking about the premiere of 4′33″..."
..
I wonder what the shipping requirements are for those Monster magnets?
..
The days of soldiers marching across bridges are long past:) Breaking step may be a tradition now, but not necessary. BUT, see https://mythresults.com/episode60
With a sufficiently large mass, a 'vibration system' might do some serious damage.
..
. .. . .. --- ....


RachelDecember 29, 2017 4:32 AM

Callmelateforsupper

Great list. but I'm itching to know what further aversions you learnt from the military!! The mind boggles. I continue to wonder how marvels such as Clive and JG4 squashed their originality into that box

CallMeLateForSupperDecember 31, 2017 11:33 AM

@Rachel
"[...] I'm itching to know what further aversions you learnt from the military!!"

I'd gladly scratch that itch, but doing so would take me much further into the weeds and possibly get me banned. (Oh what the heck; here's one more: awe of rank.)

CallMeLateForSupperDecember 31, 2017 11:42 AM

@four72
"[...[ did 'modprobe floppy' not do the trick?"

Don't remember that being a suggestion or that I tried it. Too long ago. Duly noted though (on a PostIt). Tnx.

CallMeLateForSupperJanuary 1, 2018 8:59 AM

@Wael
"[...] a G10 (whatever that means)"

Just a sort-of-educated guess: the G (tone) in the octave that is 10 above the one in which the tone A-440 (i.e. 440 Hz) resides.

I am *not* a musician, just puttered with scales in a project for my musician bro-in-law.

RatioJanuary 1, 2018 11:00 PM

@CallMeLateForSupper, @Wael,

A440 is A4, not A0, so G10 is almost 6 octaves higher.

On a piano A0 is (usually) the leftmost key, while A4 is the A above the middle C, or C4. (The octaves are taken from C up to, but not including, the next C.)

G10 is 2 semitones (“piano keys”) below A10 at 440 * 25 * 210/12 Hz ≈ 25 kHz.

WaelJanuary 2, 2018 12:17 AM

@Ratio, @CallMeLateForSupper,

210/12

Where does this term come from? 25 kHz is too high for me to hear. My hearing stops at around 12 kHz. I tested it using a Tone generator app.

RatioJanuary 2, 2018 3:15 AM

@Wael, @CallMeLateForSupper,

I assume you know that notes that are an octave apart have frequencies that are a factor 2 apart. In the standard Western tuning (called “12-tone equal temperament”), an octave is divided in 12 equal “steps”, called semitones, that each correspond to a frequency change of a factor 21/12.

This is why there are 12 piano keys in an octave and not some other number. E.g., in an octave from C to C:

C   C♯   D   D♯   E   F   F♯   G   G♯   A   A♯   B   C

C♯ or “C sharp” is up a semitone from C; on a piano it’s the black key to the right of C. (And that same black key is also to the left of D, so you can think of it as a semitone down from D and then you’d call it D♭or “D flat”. I bolded the notes that fall on black keys.)

The factors 25 and 210/12 represent the 5 octaves and the 10 semitones from A4 to G10. It’s the same thing as writing 440 * 26 * 2-2/12, to show you go up 6 octaves from A4 to A10 and then down 2 semitones from A10 to G10 (as you can see above). Maybe that would have been clearer.

RatioJanuary 2, 2018 3:34 AM

I should have said that there are 12 semitones between the 13 keys of an octave.

WaelJanuary 2, 2018 4:32 AM

@Ratio, CC: CallMeLateForSupper,

Maybe that would have been clearer.

Thanks, all makes sense now!

WaelJanuary 2, 2018 4:37 AM

@Ratio,

Did you miss an E♯ in the sequence? The keys between the two 'C's are 11. What about B♯? Or are you fudging data to fit the numbers? :-)

Clive RobinsonJanuary 2, 2018 7:15 AM

@ Ratio,

This is why there are 12 piano keys in an octave

Please,do not start singing "Doe a deer" from the Sound of Music, I know one ot the "Children" died over Xmas, but the film blighted my early television watching when the BBC would play it, "The Great Escape" or "Oliver" at Xmas or Easter every year. The sound of "Will you buy..." makes me cringe as does "Food Glorious Food...".

But for some unknown reason Ron Moody singing "You've got to pick a pocket or two" still brings a smile to my face... Strange to think the "Artfull Dodger" is "Phil Collins" in his film debut, who's later debut solo single was Something "In the air tonight" with a reasonably good drum solo...

@ Wael,

Did you miss an E♯ in the sequence?

Have a look at the pattern of black keys on a piano and you will see where the missing sharps are.

The reason for the difference is how the keys sound in the human head. In Western Culture they "feel" right. However other culrures from the Middle East east wards have different tonal spacings and sound quite unpleasant to a Western Ear.

Interestingly when you get around to the Far East spoken languages actually use the tone differences to convey information, which might acount for why nearly 20% of the respective populations are "pitch perfect". But if memory serves I've mentioned this social environment on local evolution information before. There is also a correlation between people who speak French and other Romance languages and their apparent high cheek bone look, it's down to the fact Romance languages are more from the front of the mouth and thus syllablistic in sound, where as Germanic languages are more from the back of the mouth or throat and thus guttural in sound. This causes different muscle usage which in turn changes the apparent shape of the face.

As for still hearing 12Khz you are lucky, like a lot of tall people my hearing has become deficient at an early age (environment issues again). Though my time wearing the green and being in the shooting team as well as field sports shooting has left me with tinnitus and unbalanced hearing which is in the lower frequencies, though oddly I can "feel not hear" some higher frequencies in my head bones which is realy uncomfortable. All in all it's why I don't use phones or those bluetooth ear pieces to talk to people as I only get to hear part of what is being said in each ear, oh and why I'm having to learn to lip read...

Bong-Smoking Primitive Monkey-Brained SpookJanuary 2, 2018 3:58 PM

@ Clive Robinson:

Caution: Keep the volume down. The second link song is a tad dirty - true, but dirty

However other culrures from the Middle East east wards have different tonal spacings and sound quite unpleasant to a Western Ear.

How could you say that? You have a freakin' horrible taste! Here is an Arabic song along with it's one-minute American parody version. Oh, you don't do youblube. Too bad :)

RatioJanuary 2, 2018 5:30 PM

@Wael,

Did you miss an E♯ in the sequence? […] What about B♯?

Both exist (as do double sharps, double flats, and others), but they are “the same” as F and C. I only needed a (one) name for each of the seven white and five black keys that are repeated again and again on a piano keyboard so that I could use something visual I figured you’d be familiar with to illustrate maybe unfamiliar musical ideas.

(Musical reality is much messier, but this is completely accurate as a description of this system of pitch notation.)

The keys between the two 'C's are 11. […] Or are you fudging data to fit the numbers? :-)

Heh. The problem is that the thirteenth key is called the octave (of the first), while keys one through twelve are said to be in the same octave. The octave (key number thirteen) is part of another octave (group of twelve keys with the same subscript in this notation), because that’s totally not confusing. Tough crowd. :-)

TatütataJanuary 4, 2018 10:57 AM

Old hat, here are some HDDs, FDDs, and other junk acoustically leaking information. (Are they crashing the HDD heads?)

As for the attack, when I was designing green-painted electronics there were plenty of shock and vibration specs to meet, and rather impressive vibration tables to make sure they actually were met. Loud noise shouldn't be a problem for well-designed equipment.

But I remember a colleague who came back from the field with tales of how the grunts were handling stuff, like radios casually dumped at the back of a truck and banging about.

Acoustic weapons have been fantasized about for a rather long time. The one that seems to be in operation is the one directed against humans, i.e., ear-damaging sound projectors for crowd control. :-(

Clive RobinsonJanuary 5, 2018 11:19 AM

@ Tatütata,

But I remember a colleague who came back from the field with tales of how the grunts were handling stuff, like radios casually dumped at the back of a truck and banging about.

I've been on both sides of that, and have deep in the trenches war stories from both perspectives...

Remind me to tell you about the detremental effect of "Bunny Hunting" with a tank on servo systems. Oh and sheer terror about a colision avoidence radar in a helecopter,a bridge and kbowledge of fuses...

Then how a bunch of brain dead scottish grunt "linies" nearly seperated me from my manhood by not puting stuff in the back of a landrover properly, oh and I think I've mentioned the 1KW HF TX with a rising VSWR and a Scottish Sgnt fixing it with a baseball bat applied to the backside of a cow...

Yup there are stories and then there are stories we are not supposed to tell, which is a shame as they are usually the best ;-)

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