A framework for evaluating the acoustic quality of urban open spaces is presented in this paper. An intensive program of questionnaire survey and field recording were carried out in twenty-five study sites representing six types of open spaces in Hong Kong. A total of 200 sound measurements and recordings were made and over 1,630 visitors were interviewed. The acoustic profiles of different types of open spaces were compared and the relationship between the psychoacoustic metrics including sharpness, roughness and fluctuation strength, and the perceived acoustic quality was portrayed in a 3D plot. The influence of sound level and the presence of sound source on subjective judgment are portrayed in a 2 by 2 matrix. Findings of this study highlight the importance of acoustic design which can help enhance the acoustic quality, general environmental quality and overall satisfaction of the visitors.