Learning effects in the Danish HINT

The benefit from hearing aid signal processing can be tested in the laboratory by means of a speech test, such as the open-set Hearing In Noise Test (HINT, Nilsson et al, 1994). The Danish HINT (Nielsen & Dau, 2011) consists of only 200 test sentences organised in 10 lists. These HINT lists are used heavily in the newly developed Competing Voices Test (Bramsløw et al, 2016) in which pairs of sentences are presented. Thus, reuse of the material will occur multiple times within visits. This can lead to learning of the sentences and possibly confound the test outcome. The change in performance over time has two components; 1) a practice effect from becoming more trained in the listening task (or alternatively, fatigue) and 2) a learning effect due to memorization of the specific sentences.

This poster presents practice and learning effects of the Danish HINT sentences from two experiments. In experiment 1, we used varying degrees of exposure at 3 visits with 3 weeks interval; selected lists were reused 1-9 times altogether. Ten elderly listeners were tested using a default adaptive HINT procedure aiming at 50% correct sentence score in speech shaped noise. Results showed a maximum within visit learning effect of 1.5 dB and a between visit learning effect of 1.1 dB. These effects can be attributed mainly to learning, as practice effect across varying lists was not statistically significant.

In experiment 2, we investigated the effect of exposing at 80% sentence score vs 50% score in two visits with 2 and 4 repetitions of lists. This test used 15 elderly listeners. While the previous learning effects were confirmed, there was no added learning due to the 80% sentence score exposure with its higher word recognition.

The implications of the results for future similar speech tests are discussed. Clever experimental design is proposed to compensate for practice and learning effects.