Vibron Ltd., 1720 Meyerside Dr., Mississauga, ON L5T 1A3, Canada
This method uses a two-number rating system as opposed to the single-number rating used in the STC method. The advantage of using two numbers is to distinguish between the speech- and low-frequency sound transmission loss performance. This makes the rating useful for applications involving music sources or mechanical system noise, in addition to speech-frequency applications to which the STC method is limited. The two numbers correspond to the speech-frequency performance transmission loss (SPTL) and the low-frequency performance transmission loss (LPTL). As explained in this paper, SPTL and LPTL predictions and measurements are a function of the source spectrum, the receiving-room noise criteria and the sound transmission loss data. When applied to common wall, floor, and ceiling constructions, SPTL and LPTL predictions correlate very well with measurements in the 500- and 125-Hz octave bands, respectively, thus simplifying field testing for performance verification.