When analysing Filtered IR results, on occasions i get negative curvature percentages for different measurement positions. I am aware this is due to 'errors', but what are these errors and how do i correct them?
Not errors as such, but it is not normal behaviour so might indicate a problem with the measurement. Negative figures indicate that the the T30 measure of decay gives a smaller answer than the T20 measure, which means the decay appears faster when calculated over a longer section of the response, which is opposite to the normal result. If the figures are only slightly negative it may be nothing to be concerned about, and it may also be less significant when measuring in a domestic-sized space, particularly below the room's transition frequency since RT60 measures are not really valid under such conditions.