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Hearing and speech perception are essential in social life. As our environment contains many background noises in everyday conversations, it is necessary to evaluate the noise tolerance. The Acceptable Noise Level (ANL) provides an approach to quantifying the maximum amount of background noise a listener is willing to put up with while listening to a target story without becoming tense. Exploring noise tolerance in speech perception, the study investigates how different calibration methods impact normal hearing participants’ monotic and dichotic ANL results.

This investigation utilizes a pared-sample t-test for statistical analysis, adopting a comparative observational approach. This study applied the Persian version of the typical ANL test. Two approaches have equalized the target and background stimuli: Root Mean Squared (RMS) and loudness match calibration via Adobe Audition. Using these modified materials the Most Comfortable Level (MCL), the Background Noise Level (BNL), and ANL were compared in terms of RMS and loudness match calibration. Fifty normal persons aged (18–39), under the conditions of monotic and dichotic listening, participated in this study.

The statistical analysis using a paired-sample t-test revealed no significant differences in the outcomes of the ANL test between the calibrations of RMS and loudness matching under both monotic and dichotic listening conditions (p=0.31 and p=0.67, respectively).

The study suggests that calibration procedures, namely RMS and Loudness matching, do not affect ANL in either monotic or dichotic conditions.

Music can be a favorite, annoying, or even a distracting noise. It is known that the processing of brain hemispheres is affected by the pleasantness/unpleasantness of music, which could be utilized as a signal or noise in auditory neuroscience. By using the Acceptable Noise Level (ANL) test, which is the quantification of noise tolerance while listening to a running speech, we investigated whether the pleasantness/unpleasantness of music affects the ANL results under monotic-listening and dichotic-listening conditions.

Based on the subjective scale scores, pleasant and unpleasant music (10 songs) were selected as alternatives to babble noise or running speech for testing 50 subjects for seven monotic and dichotic listening conditions.

While pleasant music changed the ANL significantly under monotic listening conditions, the higher level of babble noise was tolerated, and both characteristics of music pleasantness and unpleasantness changed ANL significantly for various dichotic conditions. The range of the ANL for dichotic conditions is wider than that for monotic conditions.

Music can affect the ANL in terms of pleasantness and unpleasantness for both monotic and dichotic listening conditions, with a greater effect on dichotic conditions, indicating the role of hemispheric specification in emotional music processing.

Music can regulate the activity of brain structures that play a significant role in emotions. The perceived emotion techniques such as dichotic listening clarify the relationships between auditory emotional stimuli and hemispheric asymmetries in the auditory modality. We examined the impact of pleasantness/unpleasantness of music by Acceptable Noise Level (ANL) as a subjective measure of listeners’ willingness to accept background noise.

In this study, 32 participants rated their pleasantness with about ten songs; then, we considered the effect of preferred pleasant and unpleasant music on dichotic music listening and acceptable background noise. There were six forced attention conditions to calculate ANL, followed by measuring the most comfortable level and background noise level for each condition.

The pairwise comparison analyses revealed significantly higher ANL in forced attention to pleasant music than to speech (p<0.004) and unpleasant music to the left ear (p≤0.05). The mean ANLs difference in 2 groups of right ear advantage and left ear advantage showed significant intra-hemispheric differences in the forced pleasant music attention than the forced unpleasant music attention conditions (p<0.007), and forced speech conditions (p=0.001), only in the left ear advantage group. In addition, the interaction between conditions and groups showed interhemispheric asymmetry.

Music valence and intra- and interhemispheric differences can affect the ANL dichotic processing and, consequently, lower noise tolerance (higher ANL) in forced pleasant music attention conditions.