Originally Posted by Laidlaw
they were square panels. eg 85mm each side.
OK, that makes more sense.
In order to investigate a microphone, by means of acoustical measurements you have to "isolate" the device under test (DUT) from disturbances. This is done by acousticians in anechoic chambers or out of doors. If you don't have that possibility you have to figure out ways to work around the problems. E.g. Using time selective measurements. Like FM.
How will different time windows affect the measurements? Do you need a larger room? Do you need to place the boundary microphone differently?
Or use another kind of microphone? (pressure)
Can difference measurements help?
After solving that, is it possible for you to make another set of measurements? May be post an IR file.
BTW. Long sweep times increases signal to noise ratio = good.