The reliability of functional gain.

This study examined the test-retest reliability of unaided and aided sound-field thresholds and the functional gain values derived from these measurements. Sound-field warble-tone thresholds were obtained at 250, 1000, and 4000 Hz from 24 hearing-impaired listeners with and without their hearing aids. Test-retest standard deviations were significantly larger for functional gain than for unaided thresholds, but only slightly and nonsignificantly larger than for aided thresholds. The variability of functional-gain measures is discussed in relation to measures of insertion gain obtained with probe-tube microphones.