| Frequency | Mean PTA [Pre ITS] | Mean PTA [Post ITS] | Improvement |
| 250 | 46.9 | 41.8 | 5.1 |
| 500 | 58.8 | 52.3 | 6.5 |
| 1000 | 63.7 | 56.5 | 7.2 |
| 2000 | 67.6 | 59.3 | 8.2 |
| 4000 | 72.7 | 67.5 | 5.2 |
| 8000 | 79.0 | 72.3 | 6.6 |