Table 4.
Clinical Question 2: Comparison of WDRC versus linear amplification on audibility outcomes.
| Citation | Condition | Compression settings | Stimuli/outcome measure | Effect size [95% CI]a | p |
|---|---|---|---|---|---|
| Gou et al. (2002) | WDRC | Threshold: 40 dB Attack time: NR Release time: NR Ratio: NR Volume control: AGC |
Warbled sinusoid threshold at 250 Hz | NR/NC |
p < .05 (favors WDRC) ns change at 3- and 5-mo. follow-up |
| Warbled sinusoid threshold at 500 Hz | NR/NC |
p < .05 (favors WDRC) ns change at 3- and 5-mo. follow-up |
|||
| Own linear | Threshold: NR Attack time: NR Release time: NR Ratio: NR Volume control: fixed |
Warbled sinusoid threshold at 1000 Hz | NR/NC |
p < .05 (favors WDRC) ns change at 3- and 5-mo. follow-up |
|
| Warbled sinusoid threshold at 2000 Hz | NR/NC |
p < .05 (favors WDRC) ns change at 3- and 5-mo. follow-up |
|||
| Warbled sinusoid threshold at 4000 Hz | NR/NC |
p < .05 (favors WDRC) ns change at 3- and 5-mo. follow-up |
|||
| Warbled sinusoid threshold at 6000 Hz | NR/NC |
p < .05 (favors WDRC) ns change at 3- and 5-mo. follow-up |
|||
| Jenstad et al. (1999) | WDRC | Threshold: 45 dB Attack time: 10 ms Release time: 200 ms Ratio: varied by DSL prescription Volume control: listener unable to adjust |
Loudness rating of shouted speech at 1 m (83 dB SPL) | NR/NC | p < .05 louder with linear than WDRC by 5/12 participants |
| Loudness rating of own voice at ear level (72 dB SPL) | NR/NC | ns | |||
| Loudness rating of classroom at 1 m (73 dB SPL) | NR/NC | ns | |||
| Linear | Threshold: NR Attack time: NR Release time: NR Ratio: NR Volume control: listener unable to adjust |
Loudness rating of average speech at 1 m (60 dB SPL) | NR/NC | ns | |
| Loudness rating of average speech at 4 m (48 dB SPL) | NR/NC | p < .05 softer with linear than WDRC by 9/12 participants | |||
| Jenstad et al. (2000) | WDRC | Threshold: 45 dB Attack time: 10 ms Release time: 200 ms Ratio: varied by DSL prescription Volume control: NR |
Dynamic range—FM tones | r = .87 [.53, .97]b | p = .001 (favors WDRC) |
| Dynamic range—environmental sounds | r = .88 [.56, .97]b | p = .000 (favors WDRC) | |||
| Dynamic range—speech | r = .96 [.84, .99]b | p = .000 (favors WDRC) | |||
| Linear | Threshold: NR Attack time: NR Release time: NR Ratio: NR Volume control: NR |
Number of participants with a normalized dynamic range—FM tones | r = .79 [.32, .95]b | p = .004 (favors WDRC) | |
| Number of participants with a normalized dynamic range—environmental sounds | r = .79 [.32, .95]b | p = .004 (favors WDRC) | |||
| Number of participants with a normalized dynamic range—speech | r = .77 [.27, .94]b | p = .005 (favors WDRC) | |||
| Marriage et al. (2005) | WDRC | Threshold: 40 dB at 200 Hz; 25 dB at 4400 Hz Attack time: 5 ms Release time: 30 ms Ratio: 1.2:1 to 3.0:1 Volume control: NR |
Articulation Index (profound) | WDRC vs. linear CL rpb = .33 [−.43, .82]c |
p = .011 (WDRC > linear CL)d |
| WDRC vs. linear PC rpb = .32 [−.44, .81]c |
p = .011 (WDRC > linear PC)d | ||||
| Linear CL | Threshold: high Attack time: 0.5 ms Release time: 50 ms Ratio: NR Volume control: NR |
Articulation Index (severe) | WDRC vs. linear CL rpb = .32 [−.66, .90]c |
p = .043 (WDRC > linear CL)d | |
| WDRC vs. linear PC rpb = .54 [−.48, .94]c |
p = .043 (WDRC > linear PC)d | ||||
| Linear PC | Threshold: high Attack time: 0.5 ms Release time: 5 ms Ratio: NR Volume control: NR |
Note. CI = confidence interval; AGC = automatic gain control; mo. = month; DSL = desired sensation level.
a
Positive effect sizes indicate that the direction of the effect favors WDRC; negative effect sizes indicate that the direction of the effect favors linear amplification.
b
Effect size r calculated using F statistic and degrees of freedom provided in the study.
c
Effect size rpb (point-biserial correlation coefficient), calculated from individual participant data provided in the study.
d
p values were calculated using the Wilcoxon signed-ranks test from individual participant data provided in the study.