Subjective evaluation of speech privacy at consulting rooms in hospitals: Relationship between feeling evoked by overhearing speech and word intelligibility score

Abstract

Many previous studies and related standards on speech privacy have adopted speech intelligibility as a subjective measure under the assumption of a strong correlation between them. Meanwhile, some studies have attempted to directly evaluate speech privacy. However, the methods used in these studies required evaluators to clearly understand what speech privacy is, while the concept of speech privacy is not widely known to ordinary people using public spaces. In the present study, questionnaire-based surveys and a listening test were conducted to clarify the relationship between speech intelligibility and speech privacy using a more suitable method for directly evaluating speech privacy. The respondents and participants were instructed to imagine a specific situation at a consulting room in a hospital because the required speech privacy depends on the situation. The questionnaire before the listening test showed that a feeling of dissatisfaction was the strongest feeling evoked by overhearing speech. Therefore, we used this feeling as a term for evaluating speech privacy performance that most people can easily accept and understand. The threshold of the feeling of dissatisfaction obtained from the listening test was compared with word intelligibility scores from our previous study. The comparison showed that the threshold of the feeling of dissatisfaction corresponds to a word intelligibility score of around 10–20% for participants with a typical sensitivity to personal information leakage through conversation. In addition, the ratio of participants who felt dissatisfaction increased with increasing background noise level under equal-intelligibility conditions.