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Problem interpreting UMIK-1 Calibration with REW 8 years 9 months ago #7610

  • mcmahongg
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Hi

I'm having difficulty interpreting the UMIK-1 calibration data and correctly measuring the signal from an acoustic calibrator using the REW SPL tool.

Hardware:
- UMIK-1
- Bruel & Kjaer 4230 Pistonphone (94 dB SPL, 1000Hz). I'm using the B&K 1/2" adapter.

Software:
REW version 5.01 Beta 12, Build 2849 on Windows 7 (32 bit).

The pistonphone doesn't give a sealed connection to the UMIK-1 so I'm using modelling clay to ensure seal. REW detects the UMIK-1 on startup and request the calibration file which it appears to load successfully. See screenshot of REW Preferences attached.

When I measure the SPL with the UMIK-1 in place in the pistonphone, in a quiet room, I get a reading of about 60 dB SPL (C) before switching on the tone. When I activate the pistonphone I get a reading of 108.7 dB SPL (C) - much higher than expected (even allowing for free field vs pressure microphone issues).

The sensitivity factor given in my UMIK-1 calibration file is -14.7 dB.

Now, 108.7-14.7 dB SPL = 94.0 dB SPL, which is the nominal pistonphone output.

So, am I doing something silly here or is there something wrong in the way REW is using the UMIK-1 sensitivity data?

thanks for any ideas

Gerry

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Last edit: by mcmahongg.

Re: Problem interpreting UMIK-1 Calibration with REW 8 years 9 months ago #7649

  • devteam
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Gerry,

I think that the issue might be with Win7 here. John mentioned back then that WinXP and Win7 have different rating. Please have a try with the latest beta that was released. It should solve that issue.

DevTeam
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Re: Problem interpreting UMIK-1 Calibration with REW 8 years 8 months ago #7650

  • mcmahongg
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Hi

Yes - I've done that. Very significant progress made with John's help:
www.hometheatershack.com/forums/spl-mete...w.html#axzz2InN88Ayf

thanks and best regards

Gerry

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