At long distances from the primary noise source (the fan) of a ventilation system, airflow generated noise from duct fittings can become the major noise problem. There exists only a limited amount of measured data on flow generated noise produced by some in-duct elements such as bends and transition pieces. This lack of data reflects the difficulty in obtaining such information from conventional measurements techniques. As an alternative to large scale data collection, attempts have been made to develop pressure-based techniques for predicting the flow generated noise in a duct. In this paper it is shown that the work of a number of investigators over a long period of time has resulted in the development of techniques for the accurate prediction of flow generated noise due to duct components.
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