The first step towards a valid diagnostic ACT test is taken, as research at IRU solves the ‘ceiling effect’ mentioned above, that is, the fact that one third of participants in the Swedish clinical trial could not complete the original STM test. Several modifications to the test were introduced to make the test easier. One important contribution was introducing ear and frequency-specific compensation for the hearing loss, based on the individual pure-tone audiogram. In this way, we ensure full audibility of the ACT stimulus throughout the frequency range of stimulation.
With the combined effect of the test modifications, all test subjects in the study were able to produce proper thresholds, and we also found that the strong relationship between the early ACT and speech-in-noise performance was intact. Finally, we extended the speech-in-noise testing with a more ’ecologically valid' test set-up, which further strengthened the ACT versus speech-in-noise relationship.