Normal speech privacy is indicated at Articulation
Index values of between 0.05 and 0.20 [4]. In this range,
concentrated effort is required to understand intruding
speech. Some describe unacceptable privacy as values
above 0.30. At AI values above 0.40, there is essentially
no privacy.
In this work we assumed SII as an index of quality both
for speech privacy and speech intelligibility. Recently
SII replaced the AI, as described in ANSI S3.5-1997