Table 7.
Clinical Question 2: Comparison of WDRC versus linear gain on speech recognition outcomes at high input levels (> 70 dB).
| Citation | Condition | Compression settings | Stimuli | Open/closed set | Presentation level/SNR | Effect size | p |
|---|---|---|---|---|---|---|---|
| Christensen (1999) | WDRC | Threshold: Low: 45–50 dB SPL Attack time: 5 ms Release time: 50 ms Ratio: Variable: 1.1:1 to 7.8:1 Volume control: listener unable to adjust during testing |
Bisyllabic spondaic words | Open | 80 dB SPL/quiet, +5, +10 SNR | NR/NC | ns across SNRs |
| Passages | Open | 80 dB SPL/quiet, +5, +10 SNR | NR/NC | ns across SNRs | |||
| Sentences | Open | 83 dB SPL (70 dB HL)/0, +5, +10, +15 SNR | NR/NC | ns across SNRs | |||
| Linear CL | Threshold: High: 75 dB Attack time: 5 ms Release time: adjustable up to 1 s Ratio: 8:1 Volume control: listener unable to adjust during testing |
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| Linear PC | Threshold: none Attack/release time: instantaneous Ratio: none Volume control: listener unable to adjust during testing |
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| 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 |
Nonsense words | Closed | 82 dB SPL/quiet (shouted speech at 1 m) | NR/NC | p < .05 (favors WDRC) |
| Nonsense words | Closed | 72 dB SPL/quiet (own voice at ear level) | NR/NC | ns | |||
| Nonsense words | Closed | 73 dB SPL/quiet (classroom at 1 m) | NR/NC | ns | |||
| Linear | Threshold: NR Attack time: NR Release time: NR Ratio: NR Volume control: listener unable to adjust |
Sentences | Open | 82 dB SPL/quiet (shouted speech at 1 m) | NR/NC | p < .05 (favors WDRC) | |
| Sentences | Open | 72 dB SPL/quiet (own voice at ear level) | NR/NC | ns | |||
| Sentences | Open | 73 dB SPL/quiet (classroom at 1 m) | NR/NC | ns | |||
| 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 |
Monosyllabic words (profound HL) | Closed | 80 dBA/quiet | NR/NC | ns |
| Words (profound HL) | Open | 80 dBA/quiet | NR/NC | ns | |||
| Words (severe HL) | Open | 80 dBA/quiet | NR/NC | ns | |||
| Common phrases (profound HL) | Open | 80 dBA/quiet | NR/NC | ns | |||
| Linear CL | Threshold: high Attack time: 0.5 ms Release time: 50 ms Ratio: NR Volume control: NR |
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| Linear PC | Threshold: high Attack time: 0.5 ms Release time: 5 ms Ratio: NR Volume control: NR |
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| Stelmachowicz et al. (1995) | WDRC | NR | Nonsense syllables | Closed | 80 dB SPL | NR/NC | ns |
| Linear | NR (conditions assessed using 2 different devices) |