Improving the Intelligibility of Aircraft PA Systems
A survey carried out by the authors on a range of commercial Jet Aircraft whilst in normal flight, found a wide variation in perceived intelligibility and operational signal to noise ratios of their on-board PA systems. Typical passenger cabin background noise levels of 80-85 dBA (100 -105 dBC) were recorded, whilst many systems were found to operate with either zero or negative S/N ratios. The results of extensive mock up testing are reported. It is shown that high frequency dispersion is a major factor contributing to the perceived intelligibility. The use of Distributed Mode Loudspeaker technology was found to bring about significant improvements in clarity & intelligibility but the effectiveness of Rasti as an accurate intelligibility descriptor under these conditions is questioned.
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