How to increase the accuracy of the measurement in cases with very high sound insulation?

To get the best results, three things are important

1.  Use sine sweep as excitation signal if you are using the new proposed standard (why will be in sections explained below)

2.  Use as long measurement duration as possible.

3.  Make sure you have as high output volume as possible from the loudspeaker. If you are using a sine sweep as excitation signal, be careful so you don’t burn up the loudspeaker. If you are using MLS-noise as excitation signal, a too high output level should be avoided to prevent artifacts from the distortion. Experiment with different levels to see what gives the best results.

This can all be done from Measurement->Settings....