fatemeh sadat ghaheri

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 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.

Navigation information is processed and stored in different brain areas such as hippocampus. Since multiple pathways has been reported between vestibular nuclei and hippocampus and also cognitive dysfunction specifically in spatial memory is induced by vestibular deficits، it can be assumed that vestibular system stimulation ameliorates spatial memory. The aim of study was to evaluate the effect of galvanic vestibular stimulation on normal individual’s spatial memory. In this experimental-interventional study، sixty 18-30-years-old women were randomly allocated in intervention and control groups. Intervention group undergone subthreshold bilateral bipolar galvanic vestibular stimulation and control group received sham stimulation. Stimulation was presented for 15 minutes. Corsi Block Tapping (CBT) test scores were compared before and after subthreshold bipolar galvanic vestibular stimulation exposure or no stimulation in each group and between groups. All test parameters were the same in both groups before stimulation (p<0. 050). There were significant improvement in block span، total score and learning score in intervention group after galvanic vestibular stimulation (p<0. 050)، no significant difference in delayed score (p=0. 600). Learning score was improved (p=0. 003) and delayed score was deteriorated (p=0. 010) in control group. Percentages of block span and total score in intervention group were significantly different compared to the other group (p<0. 050). Galvanic vestibular stimulation improves short-term and long-term spatial memory. This test may inherently have learning effect that is not influenced by stimulation.