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 9. Velocity Term U, For Dampers.
K Factor
The K factor is determined by first calculating the Strouhal number, and then referring to the
Strouhal Graph in Figure 10, or using the following separate K equations. Since the Strouhal
number is dependent upon the octave band frequency, a separate Strouhal number (St) and
K factor must be determined for each of the eight octave bands.
Strouhal number (St) = 60 F D ÷ U
Once the Strouhal numbers are calculated for each octave band, refer to Figure 10 to
determine the K factors or use the appropriate equation below to calculate the K factor
directly from the Strouhal number.
For St = ≤ 25: K = -36.3 - 10.7 Log (St)
For St = ≥ 25: K = -1.1 -35.9 Log (St)
32 Siemens Building Technologies, Inc.