Various estimates of directional microphone performance are possible, yielding a wide variety of published and advertised signal-to-noise improvements. There appears to be a growing concensus that the ratio of on-axis sound to diffuse sound (the ‘‘directivity index’’) provides the most realistic measure for real-world use of hearing aids. We undertook to measure several commercial digital and analog hearing aids, mostly of recent design, using the methods under consideration for ANSI standard adoption: anechoic polar measurements with data numerically integrated to obtain a diffuse-field directivity index estimate and direct anechoic and reverberation-room measurements. These measurements generally agreed, and showed a wide range of performance across designs.

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