Sound masking is widely used in open-plan offices for speech privacy. The present work aims to investigate the appropriate sound level of masking sounds in open-plan offices with different sounds. Three sound sources were used including white, pink, and brown noises. Listening tests were undertaken on 30 adults with questionnaire surveys. Speeches recorded in an anechoic room were played at 65 dB to subjects with masking sounds of different sound levels using a ceiling speaker. Five different sound levels were used for each masking sound such as 43, 46, 49, 52, and 55 dB. Subjects were asked to answer three questions about the degree of speech comprehension, annoyance and pleasantness. Results were analyzed using a Python program. As a result, it was found that white noise was evaluated as the most unconformable sound in terms of annoyance and pleasantness. It was also revealed that brown noise is the most appropriate sound source for masking with a sound level of 49 dB (SNR 16). Also, pleasantness was high with the masking sound level of 46 dB (SNR 19).
Chan Hoon Haan (Tue,) studied this question.