# Benefits of Auditory Training with an Open-Set Sentences-in-Babble-Noise
## 4 Discussion  
The present study aimed to test the effect of AT that simulates the challenge of daily communication: sentences spoken by different talkers amidst multi-talker background noise. The effect of this AT was tested for improving the objective and subjective speech perception of HA adult users. This was carried out by testing the generalization of the AT to different background noise (SSN) and lower-level speech perception (words). In addition, spontaneous learning and conservation of AT were tested, as well as the effect of AT duration (one versus two months). Importantly, the relationship between the individuals' pre-training speech perception and the benefit of the AT was measured. Generalization is the biggest challenge of AT, and the scientific literature reflects mixed evidence regarding the ability to successfully generalize AT to untrained speech perception tasks [7; 26; 27; 28; 29; 30; 31]. Therefore, to maximize the benefit of AT, we chose stimuli that simulate the main challenge in daily communication, which includes speech perception at the sentence level, in an open set, and accompanied by 4 TBN. This is considered synthetic training and is suggested by the literature as the most effective AT [7; 16; 32]. Indeed, the results showed that this AT was generalized to different sentences, to words (CVC words in an open set), and to different noise conditions (quiet and SSN). The AT was not generalized to DIN. This could be because this is a closed-set screening task and may be less sensitive to AT-related changes. The findings suggest that AT affects in a top-down manner, in which training with complex stimuli (sentences, 4 TBN) is generalized to simpler stimuli (words, SSN). The previous finding supports this conclusion and shows that AT of sentence level can affect and improve speech perception of both words and sentences, and AT of sentences in chatter noise can affect and improve sentences in SSN noise [7; 33; 34]. All speech perception tasks tested in the present study did not show a spontaneous learning effect when no training was made available in the first month of testing. This  
Figure 4: Prediction of the degree of change in speech perception tasks according to participants’ pre-training score in (**a**) sentences comprehension (HeBio) with SSN; (**b**) sentences comprehension (HeBio) with 4 TBN; (**c**) words comprehension (CVC) in quiet; and (**d**) digits identification (DIN). Regression analysis results in bold indicate a significant relationship. supports previous findings reported by some researchers [21; 35] and contradicts others who reported on spontaneous learning in speech perception tasks [16]. Nonetheless, it lays the ground for relating the improvement found in the speech perception tasks to the training rather than to spontaneous learning. Two additional questions in the study were related to the effect of training duration (one versus two months) and its conservation. One month of AT was enough to improve speech perception both in the trained and the untrained tasks, and an additional month of training did not add to this effect, similar to some studies [31; 36]. In addition, the conservation of the training benefits was observed two months after the end of the training in all tasks. Preservation of AT benefits was similarly observed in previous studies [26; 36; 37]. All these findings suggest that one month of AT with complex stimuli (sentences with 4 TBN) is sufficient for improving speech perception, and longer training has minimal or no benefit. Although a second month was not required for better AT, it may be required for conservation. Future studies should explore this question, as no conservation following one month of training was tested in the present study. Contrary to the objective tools, the subjective assessment did not show any change with training. It showed, as expected, worse scores in noisy conditions than in quiet and with a foreign conversation partner than a familiar one [33; 38; 39].