This paper describes the background, research questions and methodology of user studies on the integration of nonspeech sound and paralinguistic parameters in speechenabled applications. Preliminary results are summarized and future directions are discussed. Author Keywords Speech I/O; Auditory I/O and Sound in the UI; User Studies; Multimodal Mobile Communication. ACM Classification Keywords H5.2. Information Interfaces and Presentation: User Interfaces; H4.3. Information System Applications: Communication Applications.