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TOPIC: UMIK capabilities

UMIK capabilities 1 year 7 months ago #35707

  • steins
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I have just tested the UMIK I received a week ago. My laptop (Windows 10) recognizes it and I can make a recording using Audacity.

For my needs I cannot use Audacity or REW, so I am making my own program. It uses the Windows WASAPI. My program can now detect the USB audio capture devices I plug in. These include a phone/line ADC and an S/PDIF. Both of these use 48000 Hz sampling, 2 channels and 16 bit.

I can see that there is a device with UMIK in its description, but I cannot find the correct combination of parameters to use. I don't know how to get a list of capabilities, but have to select a combination and ask the WASAPI if it is supported.

So, what are the default capture parameters of UMIK (sample rate, channels and bits) ?
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UMIK capabilities 1 year 7 months ago #35715

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I think I got it. It seems that the driver doesn't like setting the shared mode to exclusive.
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UMIK capabilities 1 year 7 months ago #35798

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Glad to hear that you figured it out!

Have fun!
MiniDSP, building a DIY DSP community one board at a time.
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UMIK capabilities 1 year 6 months ago #36285

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I can now read the data from the UMIK. When letting the driver use default settings the format of the audio samples is 32-bit floating point. No problem for me, it makes things easier for later processing.

The first thing I am curious about is the number of channels. The driver reports 2. Are there 2 microphones, or is data copied from one channel to the other ? When I use the samples, shall I just sum the channels or shall I also divide by 2 ?

The other thing I am trying to figure out is the relation between the measured power level and the SPL. The calibration data doesn't seem to have all the information needed. I am thinking of this scenario:

Play a sine wave through a loudspeaker
Capture some samples and do a FFT to get a level relative to the full scale digital value
Subtract the "Sens factor"
Subtract the correction value for the frequency used
Add X to get the SPL

Where is X defined ?
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UMIK capabilities 1 year 6 months ago #36286

  • john.reekie
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I think you will find both channel to be the same, so I believe you should just use one of them.

I guess the driver is converting to floating point.

I think it should be possible to work out the level using 94, the analog gain in the UMIK and the sens factor, but the easiest way would probably be to just do an SPL measurement in REW and calibrate against that.
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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UMIK capabilities 10 months 3 weeks ago #39312

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john.reekie wrote:
I think you will find both channel to be the same, so I believe you should just use one of them.

I guess the driver is converting to floating point.

I think it should be possible to work out the level using 94, the analog gain in the UMIK and the sens factor, but the easiest way would probably be to just do an SPL measurement in REW and calibrate against that.

Hi,
Could describe the calibration procedure you mentioned here in more details? I'm trying to use "asynchronous" measurements with REW (playing WAV from HTPC, capturing with REW on laptop), but having hard time understanding how to go about calibrating MIC vs SPL level, vs dBFS value set in WAV.
Thanks.
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UMIK capabilities 10 months 3 weeks ago #39322

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Hi, I would think (not having tried it) that in that situation REW would give you the correct SPL reading - ?
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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