Assessment of speech privacy in closed spaces and multi-language environments

Speech privacy is the opposite concept to speech intelligibility and may be assessed by the predictors of intelligibility. In this study, Articulation Index, Speech Transmission Index and Early-to-Late Energy Ratio are examined through objective measurement for effectiveness in measuring speech privacy in closed spaces. Subjective measurements of human subjects are also conducted by using both English and Mandarin. The test materials applied in the experiments are a combination of single words, sentences, and conversation articles. The results are compared with the objective measurements. A new predictor defined as the Speech Privacy Index is proposed to assess speech privacy levels. Detailed investigations on language impact to speech privacy are carried out using two languages. The results indicate that the existing assessment on speech privacy in closed spaces needs to be modified; and that lanauage impact on speech privacy is evident and should be considered in the acoustic design of modern offices.