# Mic calibration files



## Guest

My apologies, I originally posted this elsewhere, but probably should have posted it here.


I am hoping to use a mic I own with REW, but this particular mic has no electronic calibration file. It does however, have all the calibration data in a paper document, in tabular and graphic format. This data could easily be keyed-in to an electronic file, if I only knew the required format acceptable to REW.

Anyone know if this is possible ? ...and what the file format might be ?


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## brucek

If you go to the download page, you can find several calibration files there.

Save it to your desktop and either append a .txt to the file or simply dump it into notepad and you'll see it's quite simple to read.

The format is *frequency (space) decibel_value*

So, from a cal file if it reads:

20 -5.50

This means at 20Hz the mic is outputting 5.5dB low.

You may start and stop at any frequency with any intervals. REW will fill in the blanks between your values. After the top value, REW will extend from that value higher.

Save the text file you create as a filename.cal file

Let me know if you have any trouble and I'll help.

brucek

edit: deleted post asking same question in other section.


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## Guest

Thank you very much, brucek.
That was exactly the info I was looking for.

I'll get back to you once I've had a chance to try it out.


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## wademarsten

Hi,

I looked at the sample Mic calibration files and they look exactly the same as the calibration file that I got from Dayton for my mic with one exception. At the very top it says *1000Hz	-39.9:sweat:. Does anybody know what that means and how the affects whether I should just read in the file or if I need to change something?

Any responses will be greatly appreciated.

Sincerely,
Wade Marsten


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## JohnM

If you scan through the file to the 1000Hz entry is it zero? As the cal file needs to be relative to something it is common to select the level at 1000Hz as the reference and adjust everything else to show relative to that 1000Hz level, so the comment at the top of the file may indicate what the 1000Hz reading was before everything was adjusted relative to that 1000Hz value.


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## UrsusMaritimus

I'm looking for a way to "calibrate" my REW + hardware to show correct SPL levels just by using the information I have:
- Microphone sensitivity 7.1 mV/Pa at 1kHz
- Microphone calibration file: deviation[dB] = f(frequency) referred to 1kHz
- Gain setting of my soundcard (RME Fireface UC) [dB]
- RMS voltage needed to reach "0dB FS"
For the RME FF-UC this is: Mic-Input, 0dB Gain: 0.775Vrms -> -10.3dB (RME) -> -13.3dBFS (REW)
-> 0dBFS => 3.58Vrms

Is there a menue where I can enter some sort of frequency independant scaling? The only way I found is to combine the above numbers into a dB-value that I add to the mic-calibration.

Any suggestions?

Thank you a lot
Mathias


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## JohnM

You could try John Reekie's method.


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## UrsusMaritimus

Thank you a lot, John.
I just had a short look into the procedure. Sounds like this is exactly what I need - and it's a lot easier than I thought.

I just did not think "out of the box": Use the SPL-calibration feature and "fake" the microphone


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