This paper reviews current methods of rating the noise produced by HVAC systems and explains why these ratings fail to be correlated with subjective opinion in many cases. An entirely new method of assigning noise ratings is proposed which is expected to provide a significantly better correlation between objective measurements and subjective response.

The proposed new rating method makes use of a revised set of noise criterion curves (RC-Curves) which have appeared for the first time in Chapter 35 of the 1980 Systems Volume of the ASHRAE Handbook. This paper also discusses the technical considerations leading to the development of the RC Curves as a replacement for the NC Curves which have been used in the past.