• Registered: 2013-11-27
  • Posts: 4

Topic: Loudness measuring with DIGICheck and other suitable programs

Hello,

I’m a new happy user of Fireface UFX. I need it for noise level (loudness) measurements of apartments. Normally the measurement and recording lasts 48 hours, so UFX is very practical because of its stand alone USB recording feature. This way only USB memory and naturally microphones are needed to make a complete set.

So collecting the data went extremely smoothly, but now I need some program to analyze and measure LAeq (dBA Leq), LAFmax, LApeak, and preferably also LAImax. Then also unweighted Leq and Lpeak would be needed as well as C weighted LCpeak.

I have no previous knowledge of any suitable programs, so if someone can advice me I would be very happy.

Because at the moment I can not invest too much money to the program, also information about freeware or low priced programs are very welcome even if they do not cover all the needed functions. Already LAeq and LApeak would do for now.

And this brings me to questions about DIGICheck. Please forgive me my possibly stupid questions and reasoning, they are do to my inexperience regarding all studio software… Beforehand I thought that I could use DIGICheck for the basic LAeq and LApeak measurements, but now it seems I was wrong, right? Bit Statistics & Noise function has A-weighted RMS, but it seems to be changing slowly with the noise content and not be analyzing the entire file length and adding all data to form true LAeq of the complete file.

Then ITU 1770 / EBU R 128 Meter seems to have Leq and Lpeak (with peak hold, infinite hold selected) functions I need, but they are ITU-weighted or unweighted and not have A-weighting, right? Please correct me if I have not understood all options this program offers.


Final probably stupid question. I thought that for programs like DIGICheck and other audio analyzing software user must enter the microphone sensitivity and the selected preamplifier gain concerning each recording. But I could not find any field where to enter this information. How can the program know the correct loudness level, when it has no knowledge of microphone sensitivity or preamp gain?

Or does the program assume that 1000mV (1V) input signal means 94dB SPL? So this way when my microphone has a sensitivity of -30,2 dB re 1V/Pa and I used preamp gain of 40 dB then the program shows values 9,8 dB higher than real values when recording? (I used this high gain because the recording was done in empty apartment and target was to analyze very quiet background noise level absent of high SPL.)

Again, It would help me a lot if some of you much more experienced people would find the time to educate me in this matter, please.

Best regards, Timo Kerminen

2 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,599

Re: Loudness measuring with DIGICheck and other suitable programs

DIGICheck's reference is (obviously) the digital level, dB FS (Full Scale). ITU 1770 etc are all referenced that way as well. If you want to measure loudness with a microphone you have to adjust/set/calculate sensitivity, levels and gains, from the analog front (mic) up to the AD converter, or use a reference set to compare.

Regards
Matthias Carstens
RME

MC's Website

  • Registered: 2013-11-27
  • Posts: 4

Re: Loudness measuring with DIGICheck and other suitable programs

Hi,

Thank you for the answer. I’m probably now about to buy noiseLAB Pro software for my use, because it seems to have suitable features. If someone is interested here is the link:
http://noiselabdk.wordpress.com/specifi … selab-pro/

Here are a few last questions to Mr. Carstens (or anyone else who have some input to this). How precise is the gain setting in UFX mic input? When calculating the correct loudness level I would like to know how much I can trust that for example the +40dB gain I normally use is really +40dB? For my use it’s within acceptable range if the precision is something like +/-0,5dB. And can you tell me if my following reasoning is correct, please? So can I calculate the correction factor for the loudness analyzing software, by just adding the UFX gain level to the microphone sensitivity, like:

Mic sensitivity   -30,2 dB  1V/Pa (I think that this can be here written -30,2dBV, right?)
+
UFX mic gain   +40dB
= total level +9,8dB over 0dBV line level (and +12 dB over 0dBu line level)

Or is there some other factors I’m not considering? Length of the mic cable is only 1,8m and cable has a cross section of 0,80mm2 (18 AWG) so there is no notable losses there. And my microphone is accurately calibrated so I really know for sure that it has that -30,2 dB re 1V/Pa (about 30,9 mV/Pa) sensitivity.


Best regards, Timo Kerminen

  • Registered: 2013-11-27
  • Posts: 4

Re: Loudness measuring with DIGICheck and other suitable programs

Hi,

I found good and still low priced calibrator from German manufacturer called ISEMcon, so I will buy it. No need for calculating the gain/sensitivity anymore.

But because UFX uses Digital gain control its settings are quite reliably repeatably, right? So calibration is valid for its gain setting even after Power off and new powering, correct?

5 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 25,599

Re: Loudness measuring with DIGICheck and other suitable programs

Correct.

Regards
Matthias Carstens
RME

MC's Website