Perceptual Discrimination and Production of the Japanese Nasal Plosive 「ん」 Preceding the Bilabial Plosives and Nasal [p, b, m] by Indonesian Learners

This study examines thoroughly the acquisition of the Japanese moraic nasal /N/ preceding bilabial environments ([p, b, m]) among 36 university-level Indonesian students from three academic years. Utilizing a methodology that combines perceptual discrimination tasks with Praat-based acoustic and articulatory duration analysis, this research investigates the interaction between L1 phonotactic constraints and L2 speech execution. The results show a distinctive dissociation between speech perception and production. Perceptually, learners achieved near-ceiling accuracy (96.7%–100%), facilitated by the existence of bilabial nasals in their L1 inventory. Acoustically, however, their production exhibited persistent segmental and temporal deviations. Participants frequently generated overlong durations—exceeding twice the native speaker baseline—and substituted non-assimilated variants ([n] and [ŋ]) for the target allophone [m], particularly in pre-nasal contexts (e.g., nanmai pronounced as [nanmai]). These production errors stem directly from native Indonesian phonotactic interference and orthographic bias from Romaji transcription. Notably, advanced fourth-year learners showed no significant convergence toward native-like acoustic norms, underscoring that high perceptual discrimination does not automatically yield native-like articulatory control. These findings highlight the necessity of incorporating explicit prosodic and allophonic training into L2 Japanese pedagogical frameworks.