A user-centered new product development process is discussed in this paper. The design of a new sports earphone is illustrated as a case study. User study methods such as questionnaires, survey, interviews and observations are used. Quantitative and qualitative methods are used to create Persona, scenario and discover user requirements. Quality Function Deployment (QFD) method is used to translate the users' requirements into technical requirements. The Analytic Hierarchy Process (AHP) is applied in QFD to quantify the user requirements, relate those elements to overall customer satisfaction goal and evaluate different design alternatives.