SPL meter strange behaviour

[oliver]

Hello John,
I am on Mac OS 10.13.6 with REW V 5.20 beta 34, with an RME UC audio interface.
I do have previously calibrated the microphone with a calibrator and have done several measurements.
It happen that when I started REW the SPL meter doesn't show any reading:

It is like has lost the calibration.

If I take a measurement the graph shows only the phase:

I do have to perform again the mic calibration to see again a curve.
I have included the logs.

Best regards,
Oliver.

 

[oliver]

Hi John,
I have generated the debug file for the Audio Interface.
Kind regards,
Oliver.

 

[John Mulcahy]

Nothing that looks relevant in the logs, one occasion where the audio system didn't provide devices it said it had available, which is odd, but shouldn't give the result you saw.

REW still thinks the input is calibrated, otherwise it would be red. The SPL values seem to be off the bottom of the graph though. If you look in the measurement Info panel for a measurement in that state what value is shown for the Data offset?

In the soundcard debug the input volume is shown as zero, although the data isn't zero since a dBFS value is shown.

 

[oliver]

Hi John,
have attached the measurements.
The first one is with the "error", the second one is after a mic recalibration.

 

[John Mulcahy]

The data offset for the error measurement is minus infinity, which explains the result but not how it could get that value in the first place. I found some old code that tried to compensate for the effect of input volume changes from the level used when the input was calibrated. That might be the culprit, particularly if the input volume reading was zero when the mic was calibrated and changed afterwards. I'll remove that code for the next beta.

 

[oliver]

Hi John,
just for more information,I didn't change the volume level.
I do have different input for different measurement setup, for example SPL or Impedance, so sometimes I change the input according to the measurement, but then everything is working well.
That behavior happen only when I close and open again REW. With the V 5.19 this doesn't happen.

Kind Regards.
Oliver.