REW beginners questions

[Schrodingers cat]

Hello everybody.
I new to using the REW software .
Basically I am using it to some acoustic measurements.
I have some basic question as follows:
1) should I do the level check in the "Preference" window every time I change my microphone position?
2) Why when doing the Level check the Input level should be -18dBFS and not -12dBFS and output around 75dB SPL?
3) As I understand the FS is 1Vrms as default. As I understand during the sine sweep in the measurement window
when I set the sweep level it will be constant through all the frequencies. And the length will determine in what frequencies steps
the sine sweep will be set. Did I understand that correctly?
4) This question is more broad but can I determine the SPL level of my output during the sine sweep?


Thank every one in advance for answering .
Have a great equalization

 

[John Mulcahy]

should I do the level check in the "Preference" window every time I change my microphone position?

No. You can check levels on the Measure dialog if you have made a very large change in position, otherwise it is not necessary.

Why when doing the Level check the Input level should be -18dBFS and not -12dBFS and output around 75dB SPL?

Recommended output is around 75 dB SPL to avoid damage to equipment and hearing, that's plenty loud enough. Input level isn't critical, for USB mics it may be below -50 dB FS, for analog mics it will depend on the input gain but can also be much lower than -18 dBFS. The -12 dBFS level is for line level measurements of electronics, e.g. a loopback cal measurement.

As I understand the FS is 1Vrms as default. As I understand during the sine sweep in the measurement window
when I set the sweep level it will be constant through all the frequencies. And the length will determine in what frequencies steps
the sine sweep will be set. Did I understand that correctly?

The full scale voltages depend on your interfaces but are only relevant when making electronic measurements. The sweep level is constant. There are no steps, frequency varies continuously during the sweep.

This question is more broad but can I determine the SPL level of my output during the sine sweep?

The result shows you the SPL plot. For that to be valid you either need to use a USB mic with a calibration file that includes mic sensitivity data (e.g. UMIK-1) or go through SPL calibration for an analog mic.

 

[Schrodingers cat]

Thank you very much for the clarifications.