Table 2.
Quiet thresholds, in dB SPL, for the stimuli used in Experiment 2 and the corresponding sensation level (SL), in dB SL, for the 90-dB-SPL overall level used for determining ITD thresholds. Because time did not allow quiet threshold tracking for participants 5, 6, 8 and 9, reference equivalent threshold sound pressure level (RETSPL, ANSI S3.6, 2010) for insert earphones (ER-3A) were used to estimate the listeners’ thresholds for the 250-Hz signal. To estimate SPL thresholds for 100–900 Hz, HL thresholds for 125, 250, 500, and 750 Hz were converted to SPL and averaged. Thus the estimated SPL thresholds are shown in parentheses next to did not test (DNT).
| Subject | Quiet threshold, overall level (dB SPL)
|
Sensation level (SL) of ITD stimuli (dB SL)
|
||||||
|---|---|---|---|---|---|---|---|---|
| 250 Hz
|
100–900 Hz
|
250 Hz
|
100–900 Hz
|
|||||
| CI ear | Non-CI ear | CI ear | Non-CI ear | CI ear | Non-CI ear | CI ear | Non-CI ear | |
| 1 | 83.4 | 33.2 | 87.9 | 41.1 | 6.6a | 56.8 | 2.1a | 48.9 |
| 2 | 79.4 | 61.4 | 77.7 | 67.8 | 10.6 | 28.6 | 12.3 | 22.2 |
| 3 | 24.0 | 7.3 | 57.7 | 34.3 | 66.0 | 82.8 | 32.3 | 55.7 |
| 4 | >90 | 77.9 | >90 | 70.4 | N/A | 12.1 | N/A | 19.6 |
| 5 | DNT (70.5) | DNT (80.5) | DNT (81.3) | DNT (90.0) | 19.5 | 9.5 | 8.7 | 0.0a |
| 6 | DNT (75.5) | DNT (60.5) | DNT (80.0) | DNT (61.3) | 14.5 | 29.4 | 10.0 | 28.7 |
| 7 | 52.6 | 65.9 | 55.8 | 69.2 | 37.4 | 24.1 | 34.2 | 20.8 |
| 8 | DNT (50.5) | DNT (40.5) | DNT (50.0) | DNT (42.5) | 39.5 | 49.5 | 40.0 | 47.5 |
| 9 | DNT (45.5) | DNT (40.5) | DNT (63.8) | DNT (45.0) | 44.5 | 49.5 | 26.2 | 45.0 |
| 10 | 29.7 | 23.0 | 39.5 | 27.1 | 60.3 | 67.0 | 50.5 | 62.9 |
| 11 | 39.8 | 73.0 | 50.8 | 80.2 | 50.2 | 17.0 | 39.2 | 9.8 |
| 12 | DNT (45.5) | DNT (25.5) | DNT (63.8) | DNT (41.3) | 44.5 | 64.5 | 26.3 | 48.8 |
| 13 | 57.2 | 50.8 | 51.2 | 47.3 | 32.8 | 39.2 | 38.8 | 42.7 |
| 14 | DNT (76.5) | DNT (61.5) | DNT (79.0) | DNT (70.3) | 13.5 | 28.5 | 11.0 | 19.7 |
| MEAN | 57.9 | 50.1 | 64.5 | 56.3 | 34.6 | 39.9 | 27.5 | 36.3 |
| STDEV | 20.0 | 22.3 | 15.2 | 18.8 | 18.5 | 22.3 | 14.1 | 16.8 |
Because participants 1, 4, and 5 had such a high threshold for the 100–900 Hz stimulus in at least one ear, ITDs could not be measured for this stimulus.