Wayne Parham Messages: 18791 Registered: January 2001
Illuminati (33rd Degree)
The biggest influence you'll see from indoors measurements is at low frequencies, and no absorbent material like cushions, wedges or padding will help. You would really need large membranes to absorb sound waves that long, which is how room damping at low frequencies is accomplished. I would assume that your indoor measurements are going to show what the speaker is doing only above about 300Hz, below that it's mostly the room.
As for signal types, I think white noise is probably fine for what you're doing. Pink noise would also work as long as you remember that the signal spectrum is not flat, so the measured spectrum should not be either. You'd hope to see exactly the same spectral balance at the measurement microphone as was presented to the amplifier.
For more informaton about signal types, pros and cons of each, see the post called "Measurement signal types".