The built in speakers aren't going to avail you for anything much below 400 Hhz. <a href="http://wiki.laptop.org/go/Sound#Speaker_Capabilities">http://wiki.laptop.org/go/Sound#Speaker_Capabilities</a> <blockquote style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;" class="gmail_quote"> The speakers in the XO are from and for cellphone speakers. They are optimized for voice, and have less quality frequency response at the low end of the spectrum. The XO speakers have a severely biased frequency response. We have recently performed a thorough analysis of the audio response curve of the machine and there is a spectacular 12dB peak between 3000 and 4500 Hz, this on all models. I suspect these are mobile phone speakers designed for voice clarity. What this means is kids will likely crank up the volume so that they can hear some of the lower frequencies. Since the physical size of the speakers prohibits any frequencies below 350 HZ, as they try to get a decent bandwidth, they will get the "membrane-against-the-casing" distortion (which has the merit of making the kids lower the volume but risks killing the speakers if done routinely). Someone on the hardware side really should look at the long term prospects for audio hardware failure and see what correction we can bring, by limiting signal output and/or equalising the output of the AD1888 (we dont know what can be done on chip...) The speakers start rolling off at about 600 Hz and are virtually worthless below 400 Hz. The hardware has a one-pole highpass filter at about 400 Hz (I forget the exact frequency but it doesn't matter much) in order to reduce the amount of useless LF energy that is presented to the speakers. The rolloff is only in the speaker path; the headphone path has flat response across the audio band. </blockquote> Just throwing the info out there. Seth <div class="gmail_quote">On Fri, Jun 27, 2008 at 3:16 PM, Edward Cherlin <<a href="mailto:echerlin@gmail.com">echerlin@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">This is wonderful. Thank you. I have been wishing for some of these features, particularly multiple sensor input and lower frequencies. Many bass and contrabass wind instruments and standard keyboard instruments go below 100 Hz. The note A above middle C (A4, MIDI 69) is 440 Hz, so four octaves below, the lowest note on a piano, is A0, 27.5 Hz, MIDI 21. (MIDI runs about five octaves above and below, beyond the limits of human hearing on the low end). It would be awesome to be able to demonstrate 32 ft and 64 ft organ pipes, which go down to five octaves below middle C, with a frequency of 8.2 Hz. You can't hear it, but you can feel it in your bones. I have seen such pipes on an organ in England, where legend has it that naughty choirboys were stuck in the very biggest to be shot up to the top and let down again on the air blowing through. <div><div></div><div class="Wj3C7c"> On Fri, Jun 27, 2008 at 11:33 AM, Arjun Sarwal <<a href="mailto:arjun@laptop.org">arjun@laptop.org</a>> wrote: > On Fri, Jun 27, 2008 at 7:14 PM, Brian Silverman <<a href="mailto:bss@media.mit.edu">bss@media.mit.edu</a>> wrote: >> hi >> >> sorry for the delay in responding... been busy. >> >>> I hear you don't have a recent XO!   Please add yourself to our >>> contributors database and we will send you a laptop asap : <a href="http://projectdb.olpc.at" target="_blank">projectdb.olpc.at</a> >>> <<a href="http://projectdb.olpc.at" target="_blank">http://projectdb.olpc.at</a>> >> >> thank you for this. I haven't added myself yet but plan on doing so in the >> coming weeks. >> >>> There's also the TurtleArt with Sensors project, which should probably be >>> merged back into the TurtleArt trunk -- you should talk to arjun sarwal >>> about this. >>> >>> <a href="http://wiki.laptop.org/go/Measure#Sensor_Input_into_Turtle_Art" target="_blank">http://wiki.laptop.org/go/Measure#Sensor_Input_into_Turtle_Art</a> >>> <a href="http://wiki.laptop.org/go/Activities#Programming" target="_blank">http://wiki.laptop.org/go/Activities#Programming</a> >>> <a href="http://wiki.laptop.org/go/Turtle_Art" target="_blank">http://wiki.laptop.org/go/Turtle_Art</a> >>> >> >> Yes, we should talk about this. My preference, if possible, is to somehow >> keep the versions separate. As I'm sure you've noticed, the design aesthetic >> of TurtleArt is quite minimalist. There are a lot of possible additions that >> were "obvious" that I ignored anyway. Sensors are a really good idea. >> However, rather than viewing them as an extension  I'd prefer to view them >> as part of an alternative version. > > Dear SJ, Brian : > > Perhaps Turtle Art could then be the 'upstream version'  and I could > maintain the 'Turtle Art with Sensors' fork ..? > > Thoughts ? > > --- > > > Dear Community: > > I have been working on a modification of Turtle Art with sensors that > works better than the version that has gone in Peru Activity pack. The > earlier one needed me to do gstreamer Kungfu to get the samples of > sensors/sound. The new version uses python-alsaaudio. When > python-alsaaudio (#6535) is included in builds getting samples(AC/DC) > from ADC becomes much easier and straightforward. > > > Also, I have been working upon re organizing the pages associated with > Measure Activity and Sensors with the aim that there should be easily > accessible information for people who visit the page. For example > educators click straight away on the educators section, people who > want to 'hack around' have access to the appropriate links..etc. > A very rough outline here <a href="http://wiki.laptop.org/go/Measure/New_temp" target="_blank">http://wiki.laptop.org/go/Measure/New_temp</a> > We can replace the main Measure page > (<a href="http://wiki.laptop.org/go/Measure" target="_blank">http://wiki.laptop.org/go/Measure</a>) once perhaps we can sufficiently > > > In particular it'd be great if someone could help in -- > * pulling off all the content on Measure page or linked off the > Measure wiki page and re-organizing it in the new format > * giving feedback or helping in the  proposed topics/sections of the > re-organized page > * help add more activities / projects around Measure sensors or Turtle > Art with (though if one sees links off the Measure page, there are > already > * exporting a relevant page set to sugarlabs wiki > > > > I hope to be doing a release soon of Measure Activity in a week or so. > It has been almost a few months late than I had planned it to be out. > I have been working on changes in the codebase that make it more > easily extensible (for example displaying more than one graphs, say > upto 5 while not letting update rate/frame rate drop too low). Other > changes that I have been working on are making it easier to read > values (in the previous version the calibrated values in terms of > voltage are not fully correct), adding support for more lower range > frequency signals to be displayed well (For example certain Health > peripheral projects are requiring to show as low as 10Hz signals) > In the future, I hope to release soon and more regularly with > incremental changes rather than a lot of changes and a long gap in > releases. > > > > > many thanks, > Arjun > > ps -- Sorry for this 'mashed up' email consisting of a lot of topics, > I hope to follow up on separate specific topics in separate threads > soon... > > >> >> Brian >> p.s. - is the XO-2 real enough yet to start thinking about? >> > > > > -- > Arjun Sarwal > <a href="http://dev.laptop.org/%7Earjs" target="_blank">http://dev.laptop.org/~arjs</a> > <a href="http://youtube.com/watch?v=SwcSEcfR464" target="_blank">http://youtube.com/watch?v=SwcSEcfR464</a> > _______________________________________________ </div></div>> Sugar mailing list > <a href="mailto:Sugar@lists.laptop.org">Sugar@lists.laptop.org</a> > <a href="http://lists.laptop.org/listinfo/sugar" target="_blank">http://lists.laptop.org/listinfo/sugar</a> > -- Edward Cherlin End Poverty at a Profit by teaching children business <a href="http://www.EarthTreasury.org/" target="_blank">http://www.EarthTreasury.org/</a> "The best way to predict the future is to invent it."--Alan Kay <div><div></div><div class="Wj3C7c">_______________________________________________ Its.an.education.project mailing list <a href="mailto:Its.an.education.project@lists.lo-res.org">Its.an.education.project@lists.lo-res.org</a> <a href="http://lists.lo-res.org/mailman/listinfo/its.an.education.project" target="_blank">http://lists.lo-res.org/mailman/listinfo/its.an.education.project</a> </div></div></blockquote></div>