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Site planning and environmental regulations may require evaluation of the environmental impact of alternate cooling methods for electric power generating stations. One alternate cooling method utilizes natural draft hyperbolic cooling towers. A study of the noise emissions from both crossflow and counterflow natural-draft hyperbolic cooling towers was undertaken as the initial phase in evaluating the potential environmental noise impact. Measured data are in substantial agreement with published noise prediction schemes [R. M. Ellis, J. Sound Vib. 14, No. 2, 171–182 (1971)]. Results of this study suggest a simplified noise prediction scheme. Accuracy of this new scheme is verified by field data. This paper compares measured and estimated noise emissions from natural-draft hyperbolic cooling towers with typical residential community noise levels. The potential impact in surrounding communities from broad-band noise emitted by natural-draft hyperbolic cooling towers is evaluated by common indices such as environmental regulations and published psychoacoustic rating methods.

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The so-called “screech”-type noise generated by railroad wheels on sharp curves was investigated. Laboratory tests confirmed by field trials have shown noise reductions of up to 15 dB in the noise radiated by excited resonant modes of vibration. Noise reductions were obtained by an application of a homogeneous damping treatment in selected areas of the wheel. Laboratory tests were performed to establish if damping by homogeneous layers was feasible and economical. Tests were performed on a resiliently suspended 550-lb forged-steel rapid-transit car wheel identical to those used in the field. Applications of homogeneous damping material with a weight ratio of damping material to steeI of 3.6% reduced the resonant amplification “Q” by a factor of 10. Field trials were conducted on electric-driven two-car-unit rapid-transit vehicles well known for their quietness. Sound measurements were conducted on the same section of curved track for a series of speeds for vehicles with and without damping material applied to the wheels.