Intelligibility Test Gone Wrong
On commissioning a large church, an acoustician decided to have intelligibility tests performed; a listener’s panel was duly created. To the acoustician’s alarm, the results were quite poor, as only a third of the tests proved satisfactory. However, after interviewing each member of the panel, the acoustician eventually found that the same proportion of listeners were illiterate!
Lesson Learned: When using a human panel, always beware of the cultural background!
On building a small school, an architect called an acoustician to define the acoustic treatment of the classrooms. Accordingly, the acoustician typically specified a suspended ceiling with an acoustic absorption coefficient of 0.7. Shortly after commissioning, a baffled architect called back the acoustician: The classrooms were highly reverberant. It turned out that the architect had picked up a suspended ceiling on its good look, and unfortunately, its absorption coefficient value was only 0.1 in the octave band of interest.
Lesson Learned: A suspended ceiling is not necessarily an absorptive ceiling!