Narrow ceiling speaker panels designed to be compatible with Armstrong\xae TECHZONE\u2122 suspended ceiling systems that include an end-flanged grill box nested in a baffle that supports a loudspeaker and associated electronics and which is nested in a flanged grill that is sized for compatibility. The roller retainer 3 also has pillars 5 each defined between the neighboring pockets 4. By mixing light from adjacent groups of pixels, striped visual artefacts are reduced. The message property information H belonging to the user as the sender and the message property information H the user as the addressee are updated in synchronism with the access to the message body information C so that it is possible to confirm the message transmission and reception situation of the message body information C by browsing the message property information H. At the time that corroboration is determined, the observation and its categorization-related and association-related information are assimilated into the knowledge base.