[IAEP] [sugar] TurtleArt, Logo, and XOs

Sun Jun 29 01:22:10 CEST 2008

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 <echerlin at gmail.com> 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 <arjun at laptop.org> wrote:
> > On Fri, Jun 27, 2008 at 7:14 PM, Brian Silverman <bss at media.mit.edu>
> 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
> > Sugar at lists.laptop.org
> > 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
> _______________________________________________
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