Level differences impact the fusion of concurrent vowels dissimilarly within versus across ears

This study investigated how level differences affect the fusion and identification of dichotically and monaurally presented concurrent vowel pairs where the vowels differed in level by 0, 4, 8, or 12 dB. With dichotic presentation, there was minimal variation in fusion and identification—vowels were nearly always fused and were identified consistently across level differences. Conversely, with monaural presentation, fusion and identification varied systematically across level differences—with the more intense vowel dominating fused percepts. The dissimilar effect of level difference for dichotic versus monaural presentation may arise from differences in energetic masking and/or divergent mechanisms underlying sound segregation and integration.