A new method for measuring the speech security of meeting rooms

Abstract

This paper describes a proposed new method for measuring the speech security of offices and meeting rooms. It is intended to assess the risk of someone who is talking in the meeting room being overheard at points outside the room, close to the outside boundaries of the room. Previous work has derived frequency-weighted speech-to-noise type measures that are well related to the perceived intelligibility and audibility of the transmitted speech. The proposed new method measures the attenuation between average levels in the meeting room and received levels at points 0.25 m from the outside boundaries of the meeting room in adjacent spaces. The average source room levels are representative of all possible talker location. The receiving points, 0.25 m from the room boundaries, can assess expected privacy at critical listening locations with minimal effect of the acoustical properties of the adjacent spaces. New measurements in 11 meeting rooms have been used to evaluate the influence of several parameters on the accuracy of the measured degree of speech security. These include: the type and number of sound sources used, and the number and location of microphones in the meeting room and the adjacent spaces. Details of the analyses will be presented.