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Current Research Projects:
1219-RP
QUALIFICATION OF DUCT RUMBLE NOISE RESULTING FROM AERODYNAMIC SYSTEM EFFECTS AT THE DISCHARGE OF A CENTRIFUGAL FAN
September 2004 – September 2006
Iowa State University
Principal Investigator, J. Adin Mann

Ductwork installed at the discharge at the discharge of a centrifugal fan must be aerodynamically designed to minimize large-scale airflow separation, reduce severe pressure differentials, and reduce duct resonance. Currently, the acoustic impact of centrifugal fan discharge duct configurations is qualitatively documented in the ASHRAE Handbook. However, the additive sound pressure levels of duct rumble as it relates to system effects are not accurately predictable in the initial design, and are not available in the Handbook.

The objective of the research is to quantify low frequency sound pressure levels and in-duct air pressure data for the centrifugal fan, supply air duct configurations now shown in the ASHRAE Handbook. The results will present the sound pressure level, and pressure data in a form suitable for inclusion to the ASHRAE Handbook for use by the HVAC industry in predicting duct rumble and system pressure effects. Additional Information 1219-RP.

1314-RP

REFLECTION OF AIRBORNE NOISE AT DUCT TERMINATIONS
September 2004 – September 2006
The Georgia Institute of Technology
Principal Investigator, Kenneth A. Cunefare

Much of the low-frequency HVAC noise in rooms is airborne noise that propagates inside ducts and is then transmitted through the duct termination into the room. Simple & accurate methods for estimating the losses of airborne noise inside ducts by the End Reflection Effect will provide the HVAC system designer with an essential, but now largely missing, element required in estimating noise emitted from duct terminations, particularly at low frequencies. Since it is at low frequencies where noise is often the subject of complaints and because low-frequency noise control treatments are costly, remedial fixes in response to complaints and/or installation of unnecessary noise control treatments may be avoided if accurate estimates of low frequency ERL values at duct terminations are used during system design. Additional Information 1314-RP.

1322-RP

PRODUCTIVITY AND PERCEPTION BASED EVALUATION OF INDOOR NOISE CRITERIA
January 2005 – June 2006
University of Nebraska
Principal Investigator, Lily M. Wang, Ph.D.
This research project will assess various indoor noise criteria systems that are currently used to evaluate the acceptability of background noise level in buildings, often caused by mechanical systems.  Subjective experiments will be run to test productivity and human perception of background noise for individuals exposed to: 1) discrete tones and 2) time-varying fluctuations in background noise spectra.  The goal is to determine how the current noise criteria systems correlate to productivity and psychoacoustic perception under the variety of systems-induced indoor noise situations.  Based on the results, suggestions or modifications to noise criteria systems may be proposed to allow the rating systems to account better for the subjective results.  The final results will have a direct impact on the information provided in the ASHRAE Fundamentals and Applications Handbooks on how mechanical system designers should quantify and diagnose background noise in spaces.  Additional Information 1322-RP.

1218-RP  (Complete -- look for the upcoming report and the Transactions were at Dallas)
NUMERICAL METHODS FOR LOW FREQUENCY HVAC NOISE APPLICATIONS
April 2004 — October 2005
University of Kentucky
Principal Investigator, Andrew Seybert

The science of acoustics and engineering noise control have traditionally been experimental disciplines due to the complexity of geometry, interactions and other factors present in real engineering systems. However, in the last few years commercial software has become available that can simulate comlex geometry and other complicating factors, thereby making it feasible to augment testing with numerical results.

The goal of this research is to develop a numerical method for rapid, cost-effective determination of insertion loss and transmission loss of HVAC duct components (e.g., plenums, lined and unlined elbows) and systems at low frequency, including the effects of source impedance, end reflections, and structural/acoustic coupling. Additional Information 1218-RP.

(Unfunded)  Room Noise Measurement
Chair:  Jerry G. Lilly

A Practical Guide to Noise and Vibration Control for HVAC System 2nd Edition
Schaffer, M.E. 2005. 
American Society for Heating, Refrigerating and Air Conditioning Engineers, Inc., Atlanta, GA.