A new laboratory test procedure is developed that evaluates the normal incidence sound transmission loss characteristics of a partial height panel. A comprehensive comparison of test data and the resulting single number ratings are made between the proposed and the existing barrier/sound transmission loss test procedures. Experimental attenuation measurements for various open-plan office configurations were in close agreement with calculated theoretical predictions using the geometrical theory of diffraction and normal incidence sound transmission loss test data. Measurements were conducted in a semi-anechoic room using a one-third octave band real time analyzer and pink noise as the test signal. The new test procedure provides one-third octave band data for complete acoustical analysis and a single number rating, called Weighted Articulation Index Average, for partial height panel comparisons.