SPL: Inconsistencies between Windows 7 and Linux

Hi,

Context:

I'm using REW beta.
Same computer (dual boot) therefore same sound card.
Same REW settings: Linux parameters exported and reimported in Windows.
Sound card is ASUS Xonar D1, analog output.
Mic is UMIK-1
Measurements at 48kHz SR using Java.
The 6 channels are set to the same volume level both in windows and in linux. It's easier to do on linux.
No effects whatsoever, no EQ, etc.

Problem:

Because of differences between the linux drivers and the windows drivers, I determined it's best to make windows measurements to create convolution filters tailored for windows instead of using the filters generated when using linux. They're not 100% compatible, particularly audible differences in SPL between channels (6) creating unbalance. One could always use the linux filters on windows but would require to adjust each channel gain separately to recenter the phantom image. It's doable with 2 channels but more complex with 6. Hence the idea to generate filters for linux on linux and filters for windows on windows.

When I make measurements on Linux, I set the SPL at 75 dB. I'm very used to it. I can tell just hearing it, I've been doing this for 2-3 months, the reported SPL is correct.

On windows, I have to crank the volume control on the AVR to just reach 60 dB for my measurements but the problem is, the real SPL is clearly at or very close to the pain threshold level: I have to get out of the room. I take 18 measurements, 3 for each channel so it's not tolerable for such a large amount of time. Additionally REW SPL meter reports around 40dB instead of 100-110 which is probably closer the real SPL.

Is there something I missing, or an issue?

linuxonly said:

On windows, I have to crank the volume control on the AVR to just reach 60 dB for my measurements but the problem is, the real SPL is clearly at or very close to the pain threshold level: I have to get out of the room

Click to expand...

Never raise the volume above a comfortable listening level. Clearly the displayed SPL figure is wrong on the Win7 installation. That might be related to the Windows input volume setting, check what it is set to for the UMIK. REW's input volume compensation might also be wrong for Win7 with current UMIKs, that OS is so old now it has been many years since REW was tested with it.

John Mulcahy said:

Never raise the volume above a comfortable listening level. Clearly the displayed SPL figure is wrong on the Win7 installation. That might be related to the Windows input volume setting, check what it is set to for the UMIK. REW's input volume compensation might also be wrong for Win7 with current UMIKs, that OS is so old now it has been many years since REW was tested with it.

Click to expand...

Thanks, John. I understand that. I've forgotten that fact.

Wondering if the culprit could be that untickable 'control input volume'...

The input volume shouldn't be active in WASAPI Exclusive mode, but you can adjust it via the Windows audio properties for the input.

John Mulcahy said:

The input volume shouldn't be active in WASAPI Exclusive mode, but you can adjust it via the Windows audio properties for the input.

Click to expand...

Thanks John, It's at 100% by default.

I seem to be having an opposite affect between windows 11 and Linux.
I do not have an SPL meter, but I thought the UMIK-1 could be used for one.
In linux, when using the SPL dialog, its reading really really low ( 18dB(C)S ).
When trying to increase spl to 75 for testing, its very very loud and I never achieve 75 (something is clearly wrong).

Same mic and same cal file in windows, shows a quiet room at 44dB(C)S where Linux had just shown 18.
Both REW preference settings (Windows and Linux) are ticked to "Control Input Volume" and both REW's have a value in that box of .551 to .559 (Sightly different, but very close)

Anyone know of something I can try to get Linux to behave?

Well I think I found my issue after much searching.
I "think" windows and linux show the input volume differently.
I came across a post that suggested someone in windows right click their mic volume slider and have it displayed in dB and not % and it shows that windows sees the UMIK-1 0dB at about 50% on its slider.
Well I didnt know how to do that in linux, so I searched that and found pulse audio volume control shows both % and dB and I noticed that when I let REW set the volume using that check box, I think its using a windows derived value of .5(ish) which in linux is actually -28dB, where as in windows a value of around .5 in REW is actually 0dB to windows.

When I changed that value to 1.0, pulse audio shows my mic as 0dB.....so I think my answer is to set it to 1.0 in REW.

I hope this helps someone else out there.....assuming this is the correct answer