Short‐duration samples of white noise were transmitted through 3 voice‐communication systems and reduced to visual spectrum displays (sonagraph sections). Likewise, samples of residual noise were taken from each system during no‐signal intervals and similarly displayed. By means of a transparent frequency‐amplitude overlay scale, S+N/N ratios were determined at the midfrequencies of the octaves between 150 and 4800 cps. These ratios were used as the basis for calculating an articulation index (AI) for each system, after the octave‐band method of Kryter. PB‐word‐articulation scores corresponding to the calculated AI's were taken from published curves; these scores compared favorably with scores obtained from tests made by transmitting PB wordlists through the three systems. Suggestions are made for refining and simplifying the octave noise‐band technique.