1D Array of Waveform

[MeCoOp]

All in all thanks for your help thus far sir, greatly appreciated!!

[Nick_F1]

Hi MeCoOp,

There are a couple of things that I see with your VI that might need to be adjusted.  First, since you are using a Task, you do not need to have the DAQmx timing vi since the timing is setup in your task.  You can either remove the task and the DAQmx Create Task.vi and replace it with the a Channel Constant and DAQmx Create Channel.vi or you can just remove the DAQmx Timing.vi.  Also, you might want to set a number of samples to read in the DAQmx Read.vi so that you will grab a set number of data each time.  When I was running your program, I would grab about a millisecond worth of data each time which might not be enough data for proper filtering.

Another thing that would help is to search for the SVL Scale Voltage to EU.vi and place that after your DAQmx read.  This will scale your voltage readings to Engineering Units, which you can set to dBA.

When you say that you read each microphone independently, are you wiring the daqmx output straight into the octave graph, and then comparing that to the averaged signal of two microphones into the octave graph?  Are both microphones pointed at the same source?

Hopefully the first paragraph will clean up your acquisition and then we can look more closely into why you are getting a lower dBA

[MeCoOp]

Nick, went ahead and removed the DAQmx timing vi as you suggested and also set a control on the DAQmx read vi.  Since my microphones are already configured in MAX I didn't see a reason to include the SVL Scale Voltage to EU vi since I assumed the conversion was done in the task I created.  Please correct me if I am wrong in the assumption.

Yes, when I reference an individual microphone read I am comparing numbers based on the method you mention.  Additonally, each mic is located in a reverb room and I use a calibrated sound source to compare readings between each mic and the "averaged" reading.  With that said I ran a test today where I read from each mic and the "averaged" mics.  I allowed the sound source to run for five minutes and then each mic aquired data for five minutes, then I collected data on each.  My first comparison was between the calculated average of each independent microphone reading to the "averaged" microphone reading which came out to be about 4% off on the whole with the "averaged" readings being consistently lower than the independent calculated average.  I then calculated the percent difference of each band reading for the independent readings which came out to be 1.1%.  I have attached both programs, maybe it is something in my structure that is causing the difference.  One thing I did notice is that the bands displayed on the individual readings was a lot different than for the "averaged" readings.  On the individual readings I got band readings from 125 - 400 and on the "averaged" 125 - 8000, both programs had the same setting at the time the test was conducted.

Ok, now that's a lot of stuff :-)....Thanks in advance for your help!!!

[MeCoOp]

Nick, did you ever find anything wrong with my solution.  I'll probably be back on this project in a couple weeks so I'm trying to get a head start since time always seems to be an issue around here.

Thanks.

MeCoOp