Classification of sound environment based on subjective response with speech privacy in open plan offices

Abstract

To implement pleasant open plan offices (OPOs) in the preference aspect based on the subjective responses of the workers, we proposed novel acoustic environment design classification criteria for speech privacy-related parameters. To this end, we created acoustic stimuli through computer simulations and surveyed the related preference responses of test participants. Then, we selected classification criteria based on the survey response results. First, field measurements were performed in two typical OPOs, and a computer simulation model was built. Twelve different sound stimuli were generated by changing the material absorption coefficient conditions for the ceiling and floor inside an office. The investigation of the noise sensitivity and satisfaction of each sound source according to the individuals indicated that the A-weighted sound pressure level at 4 m (Lp,A,S,4m) and spatial decay rate of speech (D2,S) were the major acoustical parameters that determined OPO satisfaction, with Lp,A,S,4m considered first in the OPO design stage. The Lp,A,S,4m class interval was set to 2 dB, and a new four-level classification criteria was proposed, in which the participant response rates of satisfaction were divided according to the change of Lp,A,S,4m into 25% intervals: A (≤ 46 dB), B (46 dB ≤x≤ 48 dB), C (48 dB ≤x≤ 50 dB), and D (≥50 dB). A large difference of two or more satisfaction classes was observed between the high and low noise sensitivity groups for the same Lp,A,S,4m, confirming that the noise sensitivity of workers influences the preferences for OPOs. The proposed classification criteria are expected to be applicable to the design of comfortable OPOs in the future.