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]> 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 > > 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
