The paper is the acoustical, articulatory, and physiological investigation of the phonetic changes of the "er-hua" rimes, i.e., the rimes affixed with the diminutive suffix "er" [Ä] ‘child', in Beijing Mandarin. Acoustically, all the [Ä]-suffixed rimes have a low F3 value, as an indication of being rhotacized. The other changes of the rimes after [Ä]-suffixation vary, depending on the type of component segments of the rimes. The rimes are added with a sub-syllabic [Ä], when the rimes end with a non-back vowel. When the rimes end with a back vowel, no [Ä] is added to the rimes and the whole of the rimes becomes rhotacized. For the rimes which contain a diphthong or triphthong with a final vowel element [i] or [e], the final vowel element is deleted. For the rimes which end with an alveolar [n], the nasal ending is deleted. For the rimes which end with a velar [N], the nasal ending is also deleted and the whole of the rimes is nasalized.