Tangible sound

17.05.2011 22:11

A week ago Miha Ciglar from Ultrasonic audio technologies stopped by Zemanta's new office to demonstrate the tactile user interface technology they are developing. Before we met him none of us knew this kind of development is done in Slovenia, much less practically next door. We were all curious what exactly tactile ultrasonic interface means so we invited him to show one of his prototypes to us.

You might have caught the recent article about the so-called multitouch force field presented last week in Vancouver by Texas A&M University students. If you read past the science-fiction inspired title you see that it is basically only an infrared virtual-barrier type of device. It might detect accurately the position of your fingertips in the middle of the air via beam-break sensors, but there is no touch or force involved.

Miha Ciglar demonstrating a prototype tactile ultrasound interface

On the other hand the technology from Ultrasonic audio promises that you might one day actually feel parts of the computer user interface floating in space. They achieve this via focused ultrasound. This prototype uses standard piezoelectric transducers in a fixed parabolic arrangement and can radiate around 7 W of power at 40 kHz. Of course, you can't hear those frequencies, much less feel them. But through amplitude modulation of the ultrasonic carrier wave you can achieve tactile effects.

While the focused beam is invisible and inaudible, it can have some quite macroscopic mechanical effects, as Miha demonstrated with a piece of paper. I guess you could call this a textbook demonstration of the fact that waves carry momentum.

I admit that after seeing that it took some mental effort to put my hand where the paper leaflet was in the video. The effect on my fingertips however was much less dramatic. I couldn't feel the upwards push - it felt more like wind was blowing over my skin. Perhaps the intense oscillations in the air cause faster evaporation of sweat from the skin? Miha explained that with some settings you can also feel heat, when sound wave energy is converted via friction. I opted not to try that one.

One interesting side effect of this research into tactile interfaces was the discovery that such an intense, focused beam of ultrasound exposes non-linear nature of adiabatic processes in the atmosphere. This means that the amplitude modulated carrier wave can demodulate itself in thin air. The result is a speaker that produces sound that appears to originate well away from its real source.

It might look like nothing special, but when Miha swung the parabola around and moved the focus around the room the effect was uncanny. The soundtrack of people speaking didn't help with the feeling. If you can move around you can localize the sound source pretty well and it's quite amazing to find out that you can't see anything there.

In conclusion, the effects are pretty amazing and while promising, I'm guessing this technology still has some way to go before it goes mainstream. Safety is certainly one concern. From my own experience with ultrasound I know you can find some pretty loud emitters on every step, but this works on a completely different level. I'm not usually shy around sources of electromagnetic radiation of various wavelengths, but during this presentation I couldn't help but picture early researchers wondering at pretty flashes in radium and not knowing about what the invisible rays are doing to their bodies.

Posted by Tomaž | Categories: Life | Comments »

Attack from above

12.05.2011 21:00

Recently I've seen what looked like a scan of the secure shell service on one of my servers. That in itself wouldn't be interesting enough to deserve a blog post - automated scans and brute force attacks on SSH originating from compromised hosts are common these days - except my SSH is listening on a random high port, not the default 22.

That made me curios. How did the attacker get the port right? It might be I was seen connecting to this port on some network. I do SSH from all sorts of weird connections and I wouldn't be surprised if one of them was through a compromised router.

A bit less paranoid option is that the service was found through a port scan. My firewall logging setup would alert me of any straightforward attempt of running Nmap against my host. However, a low intensity scan from different IPs would probably be indistinguishable from internet's background radiation of lost packets. I did check the logs and less than 0.5 % of TCP port space ever received a packed in the last month. So if scans are happening, they are seriously low profile.

There is the third option, and that is that someone just guessed the port. I didn't use a random generator so it stands to reason that I'm not the first one to pick that particular number.

By the way, the attack wasn't very exhaustive. All together 55 user name and password combinations were tried out. After that nothing was heard from that IP ever since. Here is the list of account that were tried and the number of passwords tried for each. Interestingly, the IP maps to a Russian provider, the server is in Slovenia, while the laboratorio and seguridad sound Spanish to me.

      1 adm
      1 admin2
      1 adrian
      1 apache
      1 clamav
      1 cyrus
      1 fax
      2 info
      1 info1
      1 ivan
      1 java
      2 jboss
      2 laboratorio
      2 linux
      2 media
      1 mysql
      1 nagios
      1 oracle
      1 personal
      1 postfix
      1 seguridad
      1 software
      1 sysadmin
      1 temp
      2 tempuser
      2 test
      2 test1
      1 test2
      1 test3
      1 test4
      1 testuser
      1 tomcat
      1 unix
      3 user
      3 user1
      1 user2
      1 user3
      2 webmaster
      4 www

Needless to say, I don't even have password authentication enabled on this public-facing service, so these simple attacks failed to do any damage. However it can serve as a reminder that security through obscurity doesn't work.

Posted by Tomaž | Categories: Code | Comments »

Broken scanner

04.05.2011 20:52

Maybe a month ago, before Zemanta moved into a new, more spacious office, I accidentally snatched our flatbed scanner by its cable and pulled it to the floor. It wasn't the first time this happened, but for the first time it landed on its USB connector. The impact forced the cable and a small piece of PCB with the female USB connector well inside the space traversed by the scanning head. Since this rendered the scanner useless for business use it ended up on the top of my pile of broken but potentially still useful stuff.

The other day I took it apart to see what can be made of it. It's a Canon CanoScan LIDE 25 based on the National Semiconductor LM9832 "Merlin" scanner-on-a-chip. Just to make it clear what kind of hardware I'm talking about: this particular model currently runs for around $50 on Amazon.com. I think it wasn't much more expensive when we first bought it.

Canon CanoScan LIDE 25 scan head

Not surprisingly, everything inside it is dedicated to reducing costs. This is the first device that I disassembled that was held together by Scotch tape! There isn't a single screw inside. The glass plate is latched to a single-piece plastic shell. Two small strips of plastic on the longer sides prevent it from getting loose and are glued to the glass with sticky tape. These strips can be simply peeled off and then all further disassembly is obvious (this project has some more disassembly instructions).

The little PCB that was causing the problem (you can see it in the back on the photo above) seems to do nothing more than connect the USB via the flexible flat cable to the scanning head. Apart from the sticky-tape this cable seems to be another weak point of this design. At some point in time it got nicked and now every time the head move it gets squashed against the sides. I'm guessing the varying resistance this causes doesn't do wonders for the linearity of the head movement. Nor for the longevity of the fragile cable.

The head itself also contains the microswitches for the buttons at the front of the scanner - when the head is anywhere else than in the extreme top position the buttons don't push against anything. Also of interest is the fact that underneath the glass plate is a black-and-white calibrating strip. The head seems to look for that before starting a scan so the scanner won't work without the glass plate in place.

Posted by Tomaž | Categories: Life | Comments »

Talking analog in Cyberpipe, part 2

02.05.2011 13:58

Back in January I announced a series of electronics-oriented talks in Kiberpipa. As you probably noticed from the lack of subsequent announcements things didn't work out exactly as planned after the first talk.

Mind you, it was not for the lack of interesting hardware projects going on in this part of the world nor people wanting to talk about them. I guess it was just a turbulent time for everyone, with new, unexpected business projects, looming deadlines and job changes all taking priorities. These all caused most talks to be postponed and, without me having replacement speakers ready to jump in, also canceled.

However, the season is not yet over, so I'm pleased to announce that there will be one more talk in the series:

The talk will be tomorrow, Tuesday, 3 May at 19:00 by Rok Štefanič from Cosylab, a Slovenian company specialized in developing control systems for particle accelerators. He is coming from a team that has supplied equipment for most major particle laboratories from around the world and has worked with such important projects as CERN's Large Hadron Collider and ITER. He will discuss the principles of accelerator and detector operation. We will hear about the associated analog electronics for signal handling and processing and how they are detecting particle loss.

The talk (in Slovenian language) will be streamed live and recorded by Kiberpipa.

Posted by Tomaž | Categories: Analog | Comments »