# Benefits of Auditory Training with an Open-Set Sentences-in-Babble-Noise
## 1 Introduction  
Auditory training (AT) is used to teach people with hearing loss to make the most of their residual hearing for speech recognition and understanding, thus improving their communication, social participation, and quality of life [1]. The AT can be performed using computer-based auditory training (CBAT) programs that involve low costs for therapists and patients [2]. During the AT, participants perform a series of AT exercises, and the benefits are assessed by comparing performance before and after the training protocols. As AT aims to improve daily communication skills, successful AT should prepare the individual for the challenge of daily discourse. This points to the stimuli to be trained and the generalization level from trained to untrained stimuli.  
AT can include analytic tasks of phoneme and syllable discrimination or synthetic tasks of words, phrases, sentences, or comprehension of paragraphs and conversation. This synthetic AT trains top-down abilities that highlight the demands required for real-world communication [3, 4]. As opposed to analytic training focusing on sub-lexical features of speech, synthetic training focuses on a more complex level of understanding speech.  
According to transfer-appropriate processing (TAP) theory [5], learning depends on compatibility between the learned and tested tasks. The stimuli used in synthetic AT resemble daily communication, so the learning benefits should be better than in the analytic [6]. Indeed, synthetic approaches have been found to be more effective than analytical ones [7].  
A second issue to consider in AT is its frequency, amount, and duration, which vary considerably between studies. AT duration ranges from less than 10 training sessions [8; 9; 10] to more than 40 [11; 12] and mostly includes less than 20 training sessions. Duration and frequency range from 15 to 90 min per session, 1-6 days per week, and up to 4-8 weeks [13]. Lastly, testing the effectiveness of AT should consider individual differences. Current AT studies are not sensitive enough to individual characteristics such as age [14; 15], the onset of hearing loss [14; 15; 16], and duration of experience with hearing aids (HA) [14; 15; 16], on top of participants' hearing ability and speech perception. All these factors may affect AT and should be tested when assessing AT benefits. In addition, it has been suggested that the subjective quality of life focused on social interactions will be affected by AT and should be measured by a self-report questionnaire [16]. Previously, it was shown that participants' baseline speech perception was positively related to their improvement in speech perception tasks following AT [17].  
The present study aimed to consider these three issues of AT. The first was to keep high compatibility between the learned stimuli (AT) and those stimuli that people encounter daily, as suggested by the TAP theory [5]. This was done using training composed of sentences spoken by different speakers, accompanied by a four-talker babble noise (4 TBN). Second, we addressed the question of frequency, amount, and duration by comparing the effectiveness of one month of AT (four times a week, a total of 16 training sessions) with two months of this training frequency (32 training sessions). Lastly, we referred to the issue of individual differences by testing the effect of individuals' baseline abilities on the effectiveness of AT, assessing it using both subjective and objective measures. To ensure that any possible effect obtained during the month of training was not the result of spontaneous learning, the participants were measured in a no-training month before training, serving as a control condition for the training. In addition, to test for a possible training-conservation effect, participants were measured again two months after completing the training.