The results for ‘suspended acoustical ceilings’ are particularly interesting and worth further discussion. The types of tiles used in UBC classrooms are known. The acoustical consultant involved in the designs of many of the classrooms considers that they are usually of ‘moderate’ acoustical performance – with noise reduction coefficient, NRC ≈ 0.55 according to manufacturers’ data – and, occasionally, of ‘high’ performance – NRC ≈ 0.9. The absorption coefficients found for ‘suspended acoustical ceilings’ in this work correspond to NRC ≈ 0.4. This indicates that suspended-acoustical ceilings in UBC classrooms provide significantly less absorption than as claimed by their manufacturers. This may be because manufacturers test product absorption in reverberation chambers with highly diffuse sound fields, whereas real classrooms have more or less non-diffuse sound fields. Another potential reason for differences between the new and existing absorption coefficients is that the former were derived from EDTs while the latter were undoubtedly derived from RT20s. As mentioned above, the absorption coefficients