Investigation of the Proper Sound Levels of Artificial Masking Sounds for the Speech Privacy in Open-Plan Offices

Abstract

The present study aims to investigate the optimum level of masking sounds which can satisfy with both the occupants and acoustical privacy. In order to this, prior investigation was accomplished to know real condition of open-plan offices using questionnaire survey to 115 people. Also, acoustic listening experiments were done to 30 people with 5 scale point questionnaire. Recorded voice was played with the output sound level of 57 dB at 1m from the directional speaker. Artificial making sounds were also radiated from the ceiling speakers using pink noise. Making sounds used in the experiments consisted of 5 different sound levels which have SNR of 10, 13, 16, 19 and 22 dB. Using questionnaire, three responses from occupants were received including speech intelligibility, annoyance of masking sounds, and overall unpleasantness. As a result, it was found that SNR 22 is appropriate for the decrease of annoyance of masking sounds and overall unpleasantness while SNR 16 to SNR 19 is considered to be suitable for the reduction of speech intelligibility and the annoyance of masking sounds.