Basic Documentation
Table Of Contents
- About this Application Guide
- Chapter 1–Introduction
- Chapter 2–Physics of Sound
- Chapter 3–HVAC Sound Sources
- Chapter 4–HVAC Sound Attenuation
- Introduction to HVAC Sound Attenuation
- Plenums
- Duct Attenuation
- Duct Takeoffs and Divisions
- Duct Silencers
- End Reflection
- Environment Adjustment Factor
- Space Effect
- Radiated Sound Attenuation
- Chapter 5–HVAC System Sound Analysis
- Chapter 6–Minimizing HVAC Sound
- Appendix
- Glossary
- Index
Appendix
This Appendix contains blank copies of certain graphs and forms that have appeared in this
document. They are intended to be copied and used for sound measurement and analysis. It
includes the following topics:
• NC and RC Curves, Tabular Listing
• NC Curve
• RC Curve
• Sound Analysis Worksheet
• Sound Measurement Worksheet
NC and RC Curves, Tabular Listing
NC Curves vs. Sound Pressure Level Decibels Tabular Listing
NC 63 125 250 500 1,000 2,000 4,000 8,000
CURVE Hz Hz Hz Hz Hz Hz Hz Hz
15
47 36 29 22 17 14 12 11
20
51 40 33 26 22 20 17 16
25
54 45 38 31 27 24 22 21
30
57 48 42 35 31 30 28 27
35
60 53 46 40 36 34 33 32
40
64 57 51 45 41 39 38 37
45
67 60 54 49 46 44 43 42
50
71 64 59 54 51 49 48 47
55
74 67 62 58 56 54 53 52
60
77 71 67 63 61 59 58 57
65
80 75 71 68 66 64 63 62
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