- <title>En grunn til å takke nei til usikker digital post</title>
- <link>http://people.skolelinux.org/pere/blog/En_grunn_til___takke_nei_til_usikker_digital_post.html</link>
- <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/En_grunn_til___takke_nei_til_usikker_digital_post.html</guid>
- <pubDate>Mon, 2 Apr 2018 13:30:00 +0200</pubDate>
- <description><p>Brevpost er beskyttet av straffelovens bestemmelse som gjør det
-kriminelt å åpne andres brev. Dette følger av (ny) straffelovs
-<a href="https://lovdata.no/dokument/NL/lov/2005-05-20-28/§205">§ 205
-(Krenkelse av retten til privat kommunikasjon)</a>, som sier at «Med
-bot eller fengsel inntil 2 år straffes den som uberettiget ... c)
-åpner brev eller annen lukket skriftlig meddelelse som er adressert
-til en annen, eller på annen måte skaffer seg uberettiget tilgang til
-innholdet.» Dette gjelder såvel postbud som alle andre som har
-befatning med brevet etter at avsender har befatning med et lukket
-brev. Tilsvarende står også tidligere utgaver av den norske
-straffeloven.</p>
-
-<p>Når en registrerer seg på usikre digitale postkasseløsningene, som
-f.eks. Digipost og e-Boks, og slik tar disse i bruk, så gir en de som
-står bak løsningene tillatelse til å åpne sine brev. Dette er
-nødvendig for at innholdet i digital post skal kunne vises frem til
-mottaker via tjenestens websider. Dermed gjelder ikke straffelovens
-paragraf om forbud mot å åpne brev, da tilgangen ikke lenger er
-uberettiget. En gir altså fremmede tilgang til å lese sin
-korrespondanse. I tillegg vil bruk av slike usikre digitale
-postbokser føre til at det blir registrert når du leser brevene, hvor
-du befinner deg (vha. tilkoblingens IP-adresse), hvilket utstyr du
-bruker og en rekke annen personlig informasjon som ikke er
-tilgjengelig når papirpost brukes. Jeg foretrekker at det er
-lovmessig beskyttelse av min korrespondanse, som jo inneholder privat
-og personlig informasjon. Det bidrar til litt bedre vern av personlig
-integritet i dagens norske samfunn.</p>
+ <title>Measuring the speaker frequency response using the AUDMES free software GUI - nice free software</title>
+ <link>http://people.skolelinux.org/pere/blog/Measuring_the_speaker_frequency_response_using_the_AUDMES_free_software_GUI___nice_free_software.html</link>
+ <guid isPermaLink="true">http://people.skolelinux.org/pere/blog/Measuring_the_speaker_frequency_response_using_the_AUDMES_free_software_GUI___nice_free_software.html</guid>
+ <pubDate>Mon, 22 Oct 2018 08:40:00 +0200</pubDate>
+ <description><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>