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TRG-TRC007-EN 39
period three
Acoustical Analysis
notes
Theoretical equations aid the analysis of some path elements, but prediction
equations based on test data and experience prevail. For example, an acoustical
lab may have measured the attenuation and regenerated sound from a number
of different types of duct elbows at various airflow rates. Data recorded from
tests is used to generate an equation that can be used to model the test data.
ASHRAE collected and developed numerous prediction equations for path
components in HVAC systems, and subsequently published them in their
Algorithms for HVAC Acoustics handbook. Similar information can be found in
the National Environmental Balancing Bureau (NEBB) publication titled Sound
and Vibration Design and Analysis.
ASHRAE algorithms are widely used and generally provide good results. When
using the algorithms, it should be remembered that they mainly come from test
data. As a result, if they are used to extrapolate beyond the test conditions, the
accuracy of the algorithms will diminish.
Algorithms for Sound-Path Modeling
Figure 44