Why Specify ASTM E477 -99 ? Comparative Review - ASTM E477 DIL Calculation 1973 to Present Day

1. Why Specify ASTM E477-99? Comparative Review - ASTM E477 DIL Calculation1973 to Present Day 3/11/05

2. ASTM E477 – Version History • Original version: 1973. • Revisions: 1980, 1983, 1984, 1989, 1990, & 1996. • Current version: 1999.

3. 1973 DIL Calculation Method Aggregate-Level Calculation  DIL is calculated @Octave band level Masks impact of each 1/3 Octave band. Duct system not well defined. Reverberation room qualification based solely on ASTM E90. Simple calculations, butLess Accurate 1980 DIL Calculation Method Aggregate-Level Calculation  DIL is calculated @Octave band level Caps 1/3 Octave band variance to 5dB max. Reduces masking effects of 1973 method. Better, but still not correct. 1996/1999 DIL Calculation Method Granular-Level Calculation  DIL is calculated @ 1/3 Octave band level Accounts for 1/3 Octave band impact  No masking effect Duct system defined  Minimum 14 gauge Reverberation room qualification based on ASTM E90 &ANSI S12.31. PD defined as ‘Total Pressure Drop’  No credit for empty duct. Most Accurate Method 1973 vs. 1999DIL Calculation Overview

4. 72.6 82.4 81.9 87.0 85.0 85.0 49.6 52.7 49.7 53.5 45.8 45.8 1973 – DIL Calculation 8.1.5 To obtain the insertion loss in octave bands add the one-third octave band sound pressure levels in each octave band with and without the test specimen in place in accordance with Fig. 3 (7). The insertion loss is obtained by subtracting the octave band sound pressure levels obtained with the test specimen in the duct system from the octave band sound pressure levels obtained without the test specimen in the duct system. Empty Duct Filled Duct DIL1973 = 87.0 - 53.5 =33.5 dB Note: Calculations based on 120-LF99 125Hz Octave band raw data.

5. 3 ∑ i=1 10 x log10 (1076.9*/10+1081.9/10+1085.0/10) 10 x 8.72 = 87.2 10 x log10 (1053.9/10+1049.7/10+1045.8/10) 10 x 5.58 = 55.8 1980 – DIL Calculation • 8.1.5 To obtain the insertion loss in octave bands, combine the three one-third octave band sound pressure levels in each octave band with and without the test specimen in place as follows: • LC = 10 log 10Li/10 Where: LC = the combined octave band level and Li= an individual one-third octave band level. Empty Duct Filled Duct * 4.3dB added to comply with maximum 5 dB variance between adjacent 1/3 octave bands as required per ASTM E477-80 Section 6.5.5. DIL1980 = 87.2 - 55.8 = 31.4 dB Note: Calculations based on 120-LF99 125Hz Octave band raw data.

6. BC +1 ∑ B=BC -1 1996 & 1999 – DIL Calculation 9.1.5 To obtain the insertion loss in octave bands, the following equation shall be used: • ILoct,cf = -10 log 1/3 10 -ILB/10 • Where: • ILoct,cf = IL in preferred octave band center frequency, and • ILB = IL in three adjacent 1/3 octave bands designated BC-1, BC, and BC+1. -10 x log10 [1/3 x (10-(76.9-53.9)/10+10-(81.9-49.7)/10+10-(85.0-45.8)/10)] Empty & Filled Duct -10 x -2.72 = 27.2 DIL1996/1999 = 27.2 dB Note: Calculations based on 120-LF99 125Hz Octave band raw data.

7. 1973 to 1999 – DIL CalculationSummary 7 dB DIL variance with identical raw data. • 1973 DIL = 34 • 1980 DIL = 31 • 1996/1999 DIL = 27 Pre-1996 calculates DIL @ Octave band level. • Aggregate-Level Calculation  Masking Effect. • Less Accurate. 1996 & 1999 calculate DIL @ 1/3 Octave band level. • Granular-Level Calculation  NO Masking Effect. • Most Accurate Method.

8. Pre-1996 versions of ASTM E477 can significantly overstate DIL. Masking effect is NOT frequency dependent. Pre-1996 silencer DIL cannot be accurately compared to Post-1996 performance. Conclusions

9. Require NVLAP accredited test data in strict accordance to the latest revision of ASTM E477 (currently 1999). Specifying AMCA 1011 Certified Silencersto ensure performance accuracy to the latest standards. Recommendations