The PLACID hemisphere microphone array provides the precisely positioned multi-point microphone arrangement required for sound power level determination to ISO 3744 and ISO 3745. The array structure ensures that all microphone positions are located on the correct hemisphere radius, at the angles specified in the standard, and that each microphone is oriented at the correct incidence angle for a free-field measurement microphone. This precision positioning eliminates a significant source of between-measurement variability in sound power determination programmes.
Without a structured hemisphere array, operators must calculate and manually position each microphone individually for every test — a time-consuming process that introduces positioning uncertainty and makes systematic comparison between successive measurements on the same source difficult. The PLACID hemisphere structure allows all 10 or 20 microphone positions to be deployed simultaneously from a single central reference point, with each position defined by the structure geometry rather than by manual placement.
The hemisphere array is designed for use with the PLACID PQ1601 (16-channel, covers all 10 positions plus 6 spare channels for source monitoring) or PQ801 (8-channel, covers positions in two groups of 5). Each microphone position in the system calibration package is individually identified to its mounting position, and the measurement uncertainty budget covers the complete 10-position system.