Reference Level or Volume, what is it?

[Timothy E Smith]

I hear the phrase "reference level" or "reference volume" in marketing and test results, what is it, does it vary among different sized systems? Is it different between music and movie aficionados? If so, how?

 

[KenM10759]

This may explain it. You have to read through, don't just look at the pretty pictures.

http://www.acousticfrontiers.com/2013314thx-reference-level/