Comparison of Ensemble vs One-Third Octave Band Averaging of Field Collected Decays

There are two allowable methods to calculate the average decay rate in ASTM E2235 - 20, "Standard Test Method for Determination of Decay Rates for Use in Sound Insulation Test Methods". The first averages the data that is presented by the sound level meter for each measurement. The second employs ensemble averaging to create one decay curve and then perform the decay rate calculation on that new curve. Historically, portable sound level meters exported a calculated reverberation time in each one-third octave band for each measurement due to lack of computing power. With the rapid increase in portable computing power, portable sound level meters can now easily perform ensemble averaging. These two methods will be compared. It will be shown that ensemble averaging will produce reliable results with far fewer decays than arithmetic averaging.