Robert A. Putnam

Noise control engineering challenges in designing power plants to meet noise limits

Noise control considerations play a vital and often pivotal role in a broad range of issues in the design of modern power plant facilities. The entire design process, from site selection, through final operational acceptance, is affected by the proper integration of the governing noise criteria, especially when relatively low levels are called for. The noise control engineer is continually challenged to justify added noise control measures, maintain adequate design margins, minimize costs, performance impacts, and design impacts, while coordinating a number of cross‐discipline interfaces ranging from marketing and sales to contracts to startup and field engineering. This paper presents an overview of the principal noise control engineering tasks involved when effectively integrating required noise control features into the design process, highlights key interface requirements, and provides notes on the practicality, safety, and maintainability of control features. Illustrative examples from the author’s e...

Acoustical design margins: Uncertainty in prediction and measurement of community noise

Compliance with regulatory requirements for sound levels in communities adjacent to industrial or power generating facilities is typically a contractual commitment, with the potential for significant financial penalties in the event of noncompliance. Uncertainties at any stage of the design, specification or prediction of plant sound level may be accounted for as part of the overall plant acoustical design margins. There are also additional uncertainties in terms of compliance sound measurement surveys, that are commonly referred to as either “test tolerance,” or “instrumentation tolerance and measurement uncertainty.” From the viewpoint of the plant equipment supplier all of the uncertainties associated with equipment design and specification are simply additive to all of the uncertainties of compliance measurements, since they all contribute to, or affect the selection of, the overall plant acoustical design margin. The discussion will address the types of uncertainties in source sound power levels and ...

Acoustical performance of power plant enclosure walls—a critical assessment of needs

The acoustical design of power generating facilities invariably requires knowledge of the transmission loss characteristics of acoustical enclosures, from component specific housings to generation buildings. Many of the composite wall configurations used by vendors are either proprietary or of such recent design that laboratory test data (TL per ASTM E90) are not available. Several factors contribute to uncertainty in the application of test data. At frequencies of 125 Hz and below, all such laboratory based test data should be considered suspect, especially since for plants in which sound emissions are heavily attenuated, the low frequencies tend to become progressively more dominant at far field positions. Thus the far field A‐weighted sound levels from power plants, especially those of low noise design, are governed by sound energy in precisely the frequency range for which the TL’s for walls and enclosures are least reliable. Further, the size and mounting of power plant walls differs significantly fr...

The uncertainty of engineering grade community noise surveys and predictions relative to two particular variables

The uncertainty inherent in the estimation of the sound power level of any noise source, coupled with the variability of assumptions regarding the modeling of typical noise sources combine to yield an A‐weighted sound level predicted uncertainty on the order of 3 dB(A). This will be related to the expected uncertainty of an Engineering Grade sound survey suggested in international standards, such as ISO 6190. However, since ISO 6190 uncertainty is intended to be the measurement uncertainty, the question arises as to how we are to evaluate such combinations of measurement and predictive uncertainties. The author will discuss and defend the view that such uncertainties are additive and will propose the method of combining these effects. The modeling variables to be considered will be confined to the nature of the distributions of the source sound power level over the surface of the actual sound source, and the effects such assumptions have when considered in conjunction with barriers.

Elements of accuracy/inaccuracy in outdoor sound level predictions using ray‐tracing models

Sound emissions play a vital and often pivotal role in a broad range of issues in the design of modern power generating facilities. The modeling of those sound emissions must be as accurate as possible in order to minimize the cost of noise control measures. This paper presents an overview of the principal components of the expected accuracy in modeling the sound emissions of sources to far field outdoor positions, including source data bounds. The relative magnitudes of the various elements of this accuracy will be discussed, and an assessment of practical expectations of achievable accuracy will be included. A comparison will be presented of preliminary results of a round robin survey involving several different computer models and a proposal will be offered for additional round robin testing.

A review of current strategies and criteria for low‐frequency noise control from combustion turbines

The environmental noise impact on neighboring communities from power generation installations containing large industrial combustion turbines is often dependent upon the level of low‐frequency sound emission. Compliance with commonly specified C‐weighted far‐field criteria can be a particular challenge. An improved knowledge of the low‐frequency sound emissions from the combustion turbine exhaust is required, as well as a design approach which accounts for the possible need for future corrective measures. Such design strategies will be defined and described together with the results of actual case histories of successful installations.

Issues in modeling outdoor acoustical barriers

In the design of power generation facilities, whether classified as ‘‘indoor’’ or ‘‘outdoor,’’ it often happens that the economic evaluation of noise control measures indicates the use of free‐standing outdoor noise barriers as part of the overall facility acoustical design. Additionally, the facility buildings and components themselves often function as acoustical barriers. Whenever such barriers are to be modeled, approximations to classical barrier theory are common. The reality of actual facility arrangements, the limitations regarding placement of acoustical barriers, and the physical or economic constraints on barrier height usually mean that the size and positions of the barriers are not optimal. Furthermore, the presence of nearby reflective surfaces, the finite width of any given barrier, and the compounding effect of successive barriers or surfaces also necessitates adjustments to ideal barrier theory. This paper will discuss a number of particular cases commonly encountered and will recommend s...

Model scale testing of outdoor noise propagation from a power plant

A proposed cogenerating power plant of 70‐MW capacity is to be located in an urban setting and will be subject to stringent environmental noise emission criteria. A four‐cell forced draft cooling tower is included in the plant design. Computer modeling of cooling tower noise propagation to affected neighboring residences involved significant uncertainties due to the complex shapes of power plant building elements and existing surrounding buildings. Without a finished facility in which to perform full‐scale field tests, the next best thing is a scale model test. This paper will discuss the specifics of the 1/20th scale test setup, materials, selection, instrumentation, test execution, some problems and some lessons learned. The results of the test will be given in terms of the differences in octave band sound‐pressure levels between an unobstructed free‐field value and the modeled in situ value, at several receptor positions. The test enabled the specification of more precise sound attenuating elements for...

Some noise control problems peculiar to nuclear generating facilities

The ability to confidently predict the noise environment in a nuclear generating facility presently under construction is complicated by the design constraints of physical layout, the shape of enclosed volumes, and compliance with safety considerations. Three particular problems are discussed. First, compliance with seismic qualifications required that HVAC fan/coil units be rigidly connected to the floor, without resilient isolators. Calculation of the structure‐borne noise transmitted into adjacent spaces is discussed. Secondly, proper control of HVAC duct‐borne noise in critical safety areas involves selection of nonstandard materials. The rigid performance criteria are discussed. Thirdly, the reverberant field decay in the highly irregular spaces inside the reactor containment building presents a unique problem. The volumes to be considered are an elliptically domed circular room and two right circular cylinders, each having another right circular cylinder centered within it for the entire height of t...