- <div class="title"><a href="http://people.skolelinux.org/pere/blog/Release_0_1_1_of_free_software_archive_system_Nikita_announced.html">Release 0.1.1 of free software archive system Nikita announced</a></div>
- <div class="date">10th June 2017</div>
- <div class="body"><p>I am very happy to report that the
-<a href="https://github.com/hiOA-ABI/nikita-noark5-core">Nikita Noark 5
-core project</a> tagged its second release today. The free software
-solution is an implementation of the Norwegian archive standard Noark
-5 used by government offices in Norway. These were the changes in
-version 0.1.1 since version 0.1.0 (from NEWS.md):
-
-<ul>
-
- <li>Continued work on the angularjs GUI, including document upload.</li>
- <li>Implemented correspondencepartPerson, correspondencepartUnit and
- correspondencepartInternal</li>
- <li>Applied for coverity coverage and started submitting code on
- regualr basis.</li>
- <li>Started fixing bugs reported by coverity</li>
- <li>Corrected and completed HATEOAS links to make sure entire API is
- available via URLs in _links.</li>
- <li>Corrected all relation URLs to use trailing slash.</li>
- <li>Add initial support for storing data in ElasticSearch.</li>
- <li>Now able to receive and store uploaded files in the archive.</li>
- <li>Changed JSON output for object lists to have relations in _links.</li>
- <li>Improve JSON output for empty object lists.</li>
- <li>Now uses correct MIME type application/vnd.noark5-v4+json.</li>
- <li>Added support for docker container images.</li>
- <li>Added simple API browser implemented in JavaScript/Angular.</li>
- <li>Started on archive client implemented in JavaScript/Angular.</li>
- <li>Started on prototype to show the public mail journal.</li>
- <li>Improved performance by disabling Sprint FileWatcher.</li>
- <li>Added support for 'arkivskaper', 'saksmappe' and 'journalpost'.</li>
- <li>Added support for some metadata codelists.</li>
- <li>Added support for Cross-origin resource sharing (CORS).</li>
- <li>Changed login method from Basic Auth to JSON Web Token (RFC 7519)
- style.</li>
- <li>Added support for GET-ing ny-* URLs.</li>
- <li>Added support for modifying entities using PUT and eTag.</li>
- <li>Added support for returning XML output on request.</li>
- <li>Removed support for English field and class names, limiting ourself
- to the official names.</li>
- <li>...</li>
-
-</ul>
-
-<p>If this sound interesting to you, please contact us on IRC (#nikita
-on irc.freenode.net) or email
-(<a href="https://lists.nuug.no/mailman/listinfo/nikita-noark">nikita-noark
-mailing list).</p>
+ <div class="title"><a href="http://people.skolelinux.org/pere/blog/Measuring_the_speaker_frequency_response_using_the_AUDMES_free_software_GUI___nice_free_software.html">Measuring the speaker frequency response using the AUDMES free software GUI - nice free software</a></div>
+ <div class="date">22nd October 2018</div>
+ <div class="body"><p><img src="http://people.skolelinux.org/pere/blog/images/2018-10-22-audmes-measure-speakers.png" align="right" width="40%"/></p>
+
+<p>My current home stereo is a patchwork of various pieces I got on
+flee markeds over the years. It is amazing what kind of equipment
+show up there. I've been wondering for a while if it was possible to
+measure how well this equipment is working together, and decided to
+see how far I could get using free software. After trawling the web I
+came across an article from DIY Audio and Video on
+<a href="https://www.diyaudioandvideo.com/Tutorial/SpeakerResponseTesting/">Speaker
+Testing and Analysis</a> describing how to test speakers, and it listing
+several software options, among them
+<a href="https://sourceforge.net/projects/audmes/">AUDio MEasurement
+System (AUDMES)</a>. It is the only free software system I could find
+focusing on measuring speakers and audio frequency response. In the
+process I also found an interesting article from NOVO on
+<a href="http://novo.press/understanding-speaker-specifications-and-frequency-response/">Understanding
+Speaker Specifications and Frequency Response</a> and an article from
+ecoustics on
+<a href="https://www.ecoustics.com/articles/understanding-speaker-frequency-response/">Understanding
+Speaker Frequency Response</a>, with a lot of information on what to
+look for and how to interpret the graphs. Armed with this knowledge,
+I set out to measure the state of my speakers.</p>
+
+<p>The first hurdle was that AUDMES hadn't seen a commit for 10 years
+and did not build with current compilers and libraries. I got in
+touch with its author, who no longer was spending time on the program
+but gave me write access to the subversion repository on Sourceforge.
+The end result is that now the code build on Linux and is capable of
+saving and loading the collected frequency response data in CSV
+format. The application is quite nice and flexible, and I was able to
+select the input and output audio interfaces independently. This made
+it possible to use a USB mixer as the input source, while sending
+output via my laptop headphone connection. I lacked the hardware and
+cabling to figure out a different way to get independent cabling to
+speakers and microphone.</p>
+
+<p>Using this setup I could see how a large range of high frequencies
+apparently were not making it out of my speakers. The picture show
+the frequency response measurement of one of the speakers. Note the
+frequency lines seem to be slightly misaligned, compared to the CSV
+output from the program. I can not hear several of these are high
+frequencies, according to measurement from
+<a href="http://freehearingtestsoftware.com">Free Hearing Test
+Software</a>, an freeware system to measure your hearing (still
+looking for a free software alternative), so I do not know if they are
+coming out out the speakers. I thus do not quite know how to figure
+out if the missing frequencies is a problem with the microphone, the
+amplifier or the speakers, but I managed to rule out the audio card in my
+PC by measuring my Bose noise canceling headset using its own
+microphone. This setup was able to see the high frequency tones, so
+the problem with my stereo had to be in the amplifier or speakers.</p>
+
+<p>Anyway, to try to role out one factor I ended up picking up a new
+set of speakers at a flee marked, and these work a lot better than the
+old speakers, so I guess the microphone and amplifier is OK. If you
+need to measure your own speakers, check out AUDMES. If more people
+get involved, perhaps the project could become good enough to
+<a href="https://bugs.debian.org/910876">include in Debian</a>? And if
+you know of some other free software to measure speakers and amplifier
+performance, please let me know. I am aware of the freeware option
+<a href="https://www.roomeqwizard.com/">REW</a>, but I want something
+that can be developed also when the vendor looses interest.</p>
+
+<p>As usual, if you use Bitcoin and want to show your support of my
+activities, please send Bitcoin donations to my address
+<b><a href="bitcoin:15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b">15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b</a></b>.</p>
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