A series of map tasks were designed to investigate whether vowel contexts and prosodic prominence may affect the realizations of the alveolar and retroflex sibilants in Beijing Mandarin and Taiwan Mandarin. Results show that the realizations of the sibilants and their contrast varied by vowel context for most speakers, and were selectively subject to prosodic conditioning for only some speakers. The /u/ vowel context was where the alveolar-retroflex contrast was the least distinct and where an enhanced place contrast was achieved for half of the Beijing Mandarin speakers under focus condition. On the other hand, /u/ was the context where some Taiwan Mandarin speakers showed confusion over the place distinction or hypercorrected in response to focal prominence.

Index Terms: focus, vowel context, Mandarin alveolar and retroflex sibilants, Beijing Mandarin, Taiwan Mandarin