The built in speakers aren't going to avail you for anything much below 400 Hhz.
http://wiki.laptop.org/go/Sound#Speaker_Capabilities 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. > Just throwing the info out there. Seth On Fri, Jun 27, 2008 at 3:16 PM, Edward Cherlin <[EMAIL PROTECTED]> wrote: > 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. > > On Fri, Jun 27, 2008 at 11:33 AM, Arjun Sarwal <[EMAIL PROTECTED]> wrote: > > On Fri, Jun 27, 2008 at 7:14 PM, Brian Silverman <[EMAIL PROTECTED]> > 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 : > projectdb.olpc.at > >>> <http://projectdb.olpc.at> > >> > >> 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. > >>> > >>> http://wiki.laptop.org/go/Measure#Sensor_Input_into_Turtle_Art > >>> http://wiki.laptop.org/go/Activities#Programming > >>> http://wiki.laptop.org/go/Turtle_Art > >>> > >> > >> 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 http://wiki.laptop.org/go/Measure/New_temp > > We can replace the main Measure page > > (http://wiki.laptop.org/go/Measure) 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 > > http://dev.laptop.org/~arjs <http://dev.laptop.org/%7Earjs> > > http://youtube.com/watch?v=SwcSEcfR464 > > _______________________________________________ > > Sugar mailing list > > [email protected] > > http://lists.laptop.org/listinfo/sugar > > > > > > -- > Edward Cherlin > End Poverty at a Profit by teaching children business > http://www.EarthTreasury.org/ > "The best way to predict the future is to invent it."--Alan Kay > _______________________________________________ > Its.an.education.project mailing list > [EMAIL PROTECTED] > http://lists.lo-res.org/mailman/listinfo/its.an.education.project >
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