Hearing aid saturation, coherence, and aided loudness discomfort.

Real-ear measurements of the aided Loudness Discomfort Level (LDL) were obtained from five hearing-impaired listeners who were fit with two Class A and two Class D linear hearing aids, each with a different saturation sound pressure level (HFA SSPL90). These measurements were obtained with 75 dB SPL continuous discourse to determine whether saturation-induced distortion contributes to the sensation of loudness. Real-ear coherence measurements made at LDL were used to determine the extent of saturation, and sound quality judgments were used to determine whether the distortion present at LDL affected sound quality. Results indicated that the SPL, coherence, and sound quality ratings obtained at LDL were all higher for Class D hearing aids with relatively high HFA SSPL90 than for Class A hearing aids with relatively low HFA SSPL90. Overall results were generally consistent with the hypothesis that distortion affects both sound quality and the perception of loudness.