The dominant sound sources in different urban spaces influence residents’ multidimensional emotional responses, and the interaction of various sound sources across temporal and spatial dimensions forms a complex sound environment. This study aims to develop a comprehensive index to quantify the emotional impacts of dominant sound sources. Through field measurements, this study classified the collected audios into four major categories (natural, social, construction, traffic) and 15 subcategories, with each sound source characterized by SPL and primary frequency. A total of 1266 questionnaires were collected from 209 participants through a web-based survey for the subjective experiment, while EEG data were obtained from 35 participants in the objective experiment. Next, by integrating acoustic indicators, subjective questionnaire responses, and objective EEG data, this study constructs the CK index using principal component analysis. CK provides a single, interpretable score of emotional impact, where lower values indicate greater calm. Results show that natural sounds consistently outperformed the other three sound types, showing the highest comfort (3.54) and pleasure (3.40) ratings on a five-point Likert scale, as well as the strongest physiological response with a parietal alpha power of 18.44 μV2/Hz. The calculated CK values for natural, social, construction, and traffic sounds were 8.73, 9.91, 10.20, and 10.29, respectively. This study contributes to quantifying the emotional impacts of urban sounds and refining noise mitigation priorities using the CK index.
Zhao et al. (2026) studied this question.