Hi MS, Thanks for all your help. Now I'm trying to learn to use TOSSIM while a can't use motes at Lab.
On Wed, Apr 23, 2008 at 3:07 AM, Michael Schippling <[EMAIL PROTECTED]> wrote: > A 6db change in signal level is one bit position in a binary value -- > 2 times the voltage (note that this is 4x the power if driven into the > same load resistance, which is why +3db is twice the perceived power). > If you have a 10 bit converter you can resolve 10 double-ings of voltage > or 60 db. Given that there is (a lot) of noise, your low end response is > probably reduced by a (at least) couple bits, so the final dynamic range > you can measure is closer to 8 bits or 48 db, with fairly bad resolution > at the low end. > > I think I've done that right anyway... > MS > > Rogério De Pieri wrote: > > > Dear MS > > > > Thanks for you grat help. > > > > I just can't understood about the range at the end of your message. > > > > Clould you give-me more details? > > > > Thanks for all > > > > PS: Sorry for my bad english > > > > RP > > > > On Sun, Apr 20, 2008 at 6:06 PM, Michael Schippling <[EMAIL > > PROTECTED]<mailto: > > [EMAIL PROTECTED]>> wrote: > > > > SPL is measured as an average of the instantaneous values you get > > from, > > for instance, a microphone. What you need to do is sample the mic at > > some > > reasonable rate (making some assumptions about the frequency range > > you are > > interested in). In T1 there is a HighFrequencySampling demo app that > > sorta > > does this. > > > > Then the (sl)easiest thing to do would be to look for max values > > over a moving > > window of some large number of samples. The real way to do it would > > be to > > estimate a zero crossing point -- probably at about 1/2 the ADC > > range (what > > you get from a mote ADC is fundamentally an AC signal with a fixed > > DC offset), > > do a full-wave bridge around that zero crossing, and then an RMS > > average of > > the result (again with a moving window of some size which will > > capture the > > lowest frequency of interest). > > > > In either case you should probably do the SPL conversion on the mote > > and > > only send the results because it markedly reduces the bandwidth of > > the > > data you need to send. > > > > In order to get an engineering measurement in dBm you need to > > calibrate your averaged data against a known source and perhaps make > > some adjustments for > > the non-flat frequency response of the microphone, then convert the > > measurements to a log scale. Note that you will have some noise > > floor that > > makes the lower couple of bits insignificant, and that the max you > > can get is > > 10 to 12 bits (for Atmega and MPS converters). This means 8-10 > > significant > > bits where each bit is 6dB (a doubling of sound pressure), so your > > measurement > > range is at best somewhere between 48 and 60 dBm. Hopefully that is > > sufficient > > for your system... > > > > MS > > > > Rogério De Pieri wrote: > > > > Hi dear all > > > > I am working on an acoustic project within tinyos-2.x > > environment. The goal of the project is to take a view of the > > distribution of SPL (Sound Pressure Level) in an ambience. > > > > > > I took just a few of steps on that, and a this time I'm looking > > for documentation about how to take datas from acoustic/sound > > sensor from sensorboards. > > > > Another problema I know I will have is to turn de sound or > > acoustic data in SPL or dB. > > > > > > Does anybody caan help me? > > > > Thanks for all > > > > > > -- > > > > > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > Tinyos-help mailing list > > Tinyos-help@millennium.berkeley.edu > > <mailto:Tinyos-help@millennium.berkeley.edu> > > > > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > > > > > > -- Platform: WinXP/Cygwin > > TinyOS version: 1.x, Boomerang > > Programmer: MIB510 > > Device(s): Mica2, MicaZ, Tmote > > Sensor board: homebrew > > > > > > > > > > -- > > > > > > ------------------------------------------------------------------------ > > > > _______________________________________________ > > Tinyos-help mailing list > > Tinyos-help@millennium.berkeley.edu > > https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help > > > -- Rogério De Pieri (Lelo) Buscando melhorar a cada dia Áudio, Hardware & Software Fone: (48) 8409-0575
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