The Jumppa
Posted 15.01.12 by ajv
Theoretical living room acoustics - New Formula
Posted 26.12.11 by ajv
Just came across a paper where different ad hoc formulae for predicting rectangular room reverberation time are compared with actual measurements: R. Neubauer et al: Prediction of the Reverberation Time in Rectangular Rooms with Non-Uniformly Distributed Sound Absorption
In the paper, Neubauer et al also derive a “New Formula” with improved accuracy, given in equations 20-21. It seems though that the equation 21b has a typ’o negative sign prefix that seems a bit off. Anyway, I wrote a Matlab code to test it:
Haven’t tested it yet, but seems to give a figure in the same ballpark with my measurements by just picking the absorption coefficients with the Stetson-Harrison method. Now if I get to test this more with actual absorption data (available here for some basic materials and here for Ecophon Master SQ) and one could see the differences not unlike my high fidelity measurements, that’d be something. But it’s getting late already…
Update 26.12.2011 14:30. And the same in your favorite browser, caveat emptor still applies:
Practical living room acoustics - phase 1 preliminary results
Posted 21.12.11 by ajv
Finally got the Ecophon Master SQ elements (600 × 1200 × 40 mm, 23 in total) installed on the living room walls. Here is some preliminary reverberation time (RT60) measurements using high fidelity N900 microphone and Matlab software
This is how it sounded like:
Impulse response in living room before acoustic conditioning 20.12.2011
Moved the couch to the center of the room before installing the acoustic elements. This increases RT since the hardwood floor along with the room corner are exposed adding to the reflections. Results:
Analyzed 13 sounds, mean RT60 = 1.471586 +/- 0.118441, median RT60 = 1.461902
Installed the elements, couch still in the center of the room. This is how it sounded like:
Impulse response in living room after phase 1 acoustic conditioning 21.12.2011
Rt60 Results:
Analyzed 15 sounds, mean RT60 = 0.989894 +/- 0.049873, median RT60 = 0.985948
The difference is very audible, even by the better half. Hooray.
To be continued…
More practical living room acoustics
Posted 7.12.11 by ajv
Making the living room more cozy acoustic wise is getting closer. I ended up deciding to put Paroc Royal or Ecophon Master SQ up on the walls near the ceiling.
I did some planning using Google Sketchup, just to see how 1200×600 elements would fit in there.
Here the smaller gap between the elements is 10 mm (in the groups of four) and 90 mm between the groups.
Also found out how to display Google Sketchup models in iPad:
- Get a STL-exporting plugin
- Figure out how to install plugins (hint: place the Ruby scripts inside the directory given by Sketchup.find_support_file(“plugins”) in the Ruby console (Tools menu -> Ruby Code Editor -> Show Ruby Console (monkey wrench icon, just as you would guess)
- Get a Dropbox account
- Place the STL-model in Dropbox
- Get MeshPad app for iPad
- Get Dropbox app for iPad
- In the Dropbox app, open the STL model
- Dropbox app does not know what to do with it, push the arrow icon (the one that looks not unlike the share/tweet icon)
- Victory
Easy as 1 2 3 4 5 6 7 8 9
helistin.fi terve24.fi, huoltamo.com etc password analysis
Posted 28.11.11 by ajv
Now that the passwords and user names have been compromised for the above mentioned sites, we get a look into passwords differences in health-related and pre owned car sales sites .
This time around the username and passwords match in around 1600 cases (approx 2%). Salasana is the most popular one, but qwerty is left out of the top 20. Surprisingly enough, anneli is again the top 20.
| # | password | number of occurrences |
|---|---|---|
| 1 | salasana | 190 |
| 2 | aurinko | 145 |
| 3 | johanna | 123 |
| 4 | vauva | 91 |
| 5 | nallepuh | 78 |
| 6 | 123456 | 76 |
| 7 | susanna | 74 |
| 8 | mansikka | 72 |
| 9 | rakkaus | 67 |
| 10 | katariina | 61 |
| 11 | pauliina | 59 |
| 12 | mussukka | 59 |
| 13 | emilia | 58 |
| 14 | terveys | 57 |
| 15 | tiikeri | 56 |
| 16 | hannele | 51 |
| 17 | kukkanen | 50 |
| 18 | enkeli | 50 |
| 19 | helistin | 49 |
| 20 | anneli | 49 |
netcar.fi password analysis
Posted 16.11.11 by ajv
As the netcar.fi username and password database with around 12000 records was compromised earlier today, I thought it’d be fun to run a simple analysis to see how many usernames and passwords match and on the other hand get the list of most used passwords. The results:
611 (about 5%) usernames and passwords match, and the most common passwords are:
| # | Password | Number of occurrences |
|---|---|---|
| 1. | 123456 | 35 |
| 2. | salasana | 28 |
| 3. | bemari | 15 |
| 4. | perkele | 14 |
| 5. | auto | 14 |
| 6. | 1234 | 14 |
| 7. | mattisili | 11 |
| 8. | netcar | 10 |
| 9. | juhani | 10 |
| 10. | antero | 10 |
| 11. | yamaha | 9 |
| 12. | rasmus | 9 |
| 13. | johannes | 9 |
| 14. | ilmari | 9 |
| 15. | anneli | 9 |
| 16. | sierra | 8 |
| 17. | oskari | 8 |
| 18. | kissa | 8 |
| 19. | toyota | 7 |
| 20. | qwerty | 7 |
Used motorbikes cheaper in fall - a case study
Posted 15.09.11 by ajv
View larger.
iMac day 400+
Posted 29.06.11 by ajv
Hard disk failure. The system began to lag / stall and finally did not even boot. When booted in verbose mode (press cmd + v at startup), it was evident that at least the book keeping of the disk had gone corrupt.
The standard OS X Disk utility, which displays SMART. status would say the disk is “verified” and reported no errors with it. After starting the thing from OS X DVD and restoring from an old backup (a 2 days old back up could not be restored), the disk structure seemed also ok. However, comparing Disk Utility’s results with SMART utility revealed that the SMART status is in the eye of the beholder
I called the local Apple hotline, who told it’s better to send the thing to authorized service partner, who would charge 150-200€ for disk replacement. I also went to a PC shop where, when asked if they could replace a iMac HDD, they told me “Oh sure, is it a laptop, we’ll charge 25-75€”. Based on these, and especially the friendly guy at Apple hotline who specifically told me not to try replacing HDD myself, I decided to buy a Samsung 103SJ 1 TB disk and dig my torx drivers to broad day light.
Replacing the disk was a lot easier I thought it would. There is a very good tutorial available at ifixit . I even cut it a bit short and did not detach other cables between the motherboard and display than the vertical sync ribbon.
However, after replacing the old Hitachi 1TB HDE721010 SLA330 disk with the Samsung the HDD fan would start to make noise not unlike a normal PC. Apparently the factory installed hard disks in iMacs (late 2009 models and newer) have Apple’s proprietary firmware and read the HDD temperature not through SMART but through a separate thermal sensor connector.
I could not get that to work with the Samsung HDD (actually the connector would not fit like ifixit documentation advises). The noise issue was resolved by installing a piece of software, HDD Fan Control, which allows for manual tweaking of fan speed as a function of HDD temperature. And this thing gets the temperature through SMART and not by some proprietary means. The only downside was the price tag, about 30 € for such a small piece… But worked like a charm.
It still beats me, why I could not use my latest Time Machine backup to restore the system. I managed to get the disk to the state it was on 2nd of January 2011 and right now I’m restoring the home directory from the latest backup, which seems to run fine so far 55 GB / 171 GB.
Google Home View has no respect for privacy
Posted 9.04.11 by ajv
See this .
Requires a recent and decent browser with WebGL support ie. not IE.
Comment [3]
Matlab clone on your browser
Posted 26.09.10 by ajv
Now if someone came up with implementation that supports plot() through Google Visualization API or something.
Comment [1]
ADHD-instituutin aivosähköposti
Posted 20.09.10 by ajv
Sekos ADHD-instituutin aivosähköposti,
kun Pekka Erik Auvinen kakskakkosensa osti.
Hura-huh-hah-hei!
Holmlundi haulikoille,
lahtas Kauhajoen Matti toistakymmentä.
N8 turns any screen to touch screen
Posted 20.09.10 by ajv
Police pursuit on route 5
Posted 13.09.10 by ajv
Savon sanomat has the “video”:http://www.savonsanomat.fi/uutiset/savo/tuntien-takaa-ajo-päättyi-laukauksiin-siilinjärvellä/598026
… apparently there is something wrong with this textpattern CMS and links containing scandinavian characters or something.
Comment [2]
YLE Areena available on Playstation 3
Posted 13.09.10 by ajv
YLE Areena is now available straight from the PS3’s main menu. Tried to watch the documentary about shabby Detroit but watching stopped at least 6 times and required refreshing…
Sony releases new stupid piece of shit that doesnt fucking work
Posted 27.08.10 by ajv
Sony Releases New Stupid Piece Of Shit That Doesn't Fucking Work
Using myLogger / traxmeet on Mac OS X
Posted 21.07.10 by ajv
The mylogger GPS device used by traxmeet service is the same as i-gotU There is a command-line & GUI hack for it called igotu2gpx which works in Linux and OS X. I could download tracks with Mac but cannot erase the memory…
Best of Gosteleradio
Posted 10.07.10 by ajv
1. Market economy
2. Jews in the oven
or
1. Market economy
2. Airplanes crash into skyscrapers
or
1. Socialism
2. Peace love and happiness
Another great example of quality journalism from YLE: Mennyttä etsimässä: Hyvinvointivaltion loppu?. Unfortunately the climate change was missing from the list of the direct market economy consequences.
Comment [1]
More reverberation time measurement applications
Posted 15.05.10 by ajv
A while ago I wrote a reverberation time RT60 measurement application on Matlab. Not everyone has Matlab, but almost everyone has a Mac, so I wrote a new app for measuring RT60 in Quartz Composer which is distributed with every recent Mac computer.
The algorithm on the Matlab version is a lot smarter, with all the least squares fitting while this new one has more emphasis on the outlook and having a simpler algorithm:
Check out an example usage run on Vimeo. I was actually hoping that this would be runnable straight from this web page, but reading audio devices is unfortunately banned in web deployment.
The app is downloadable here
Hayseed Dixie at Henry's Pub
Posted 7.05.10 by ajv
Great performance. Go see on youtube if you don’t know what they’re about.
Syanidia, suolahappoa ja kukkivaa sekaihoa
Posted 3.05.10 by ajv
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