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
Chapter 3–HVAC Sound Sources
Figure 11. K versus Strouhal Number for Elbows.
Once the Strouhal numbers are calculated for each octave band, see Figure 12 to obtain the
K factors. The K factors may also be calculated using the following formulae:
For elbows with turning vanes:
K = - 47.5 - 7.69 (Log St)
2.5
For elbows without turning vanes:
K = - 9.22 - 16.48 (Log St) - 5.05 (Log St)
2
Example Elbow Sound Power Level Calculation
Determine the net sound power level that a mitered rectangular elbow will produce in a 36
inches wide x 24 inches high supply system duct with 12,000 cfm. The elbow has 15 single-
thickness turning vanes with a 9.5-inch cord length.
36 Siemens Building Technologies, Inc.