Not so much directly. The different graphs seem to be not completely equally spaced. This could be either due to compression (of the speakers or the mic) or simply because the level steps have not been exactly equal, I don't know. If you are after detecting compression effects, knowing the absolute level is at least helpful for means of comparison.I did some measurements using a single sweep signal at different levels with the iMM-6 in REW and they all look very similar. So does level affect results significantly?
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But since we are dealing with 2 channel audio and don't care about THX reference levels, there is no need for absolute level measurements, that's true.
I was thinking about something else in the first place. Some RC systems are using other signals to make sure there's enough acoustic energy in the room. But it doesn't really matter much in the context of this discussion, so I don't want to dive deeper in this topic.