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Jun 1979

Volume 65, Issue S1, pp. S2-S142

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back to top Session X. Noise III: Transportation/Environment
Contributed Papers
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Excess attenuation or impedance of common ground surfaces characterized by flow resistance (A)

J. E. Piercy and T. F. W. Embleton

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S63-S63 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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The excess attenuation due to the presence of the ground has been measured at several different sites using two fixed configurations of point source and receiver. These were source height 1 ft, and receiver location either 1.5 ft high at 25 ft from the source, or 4 ft high at 50 ft. Assuming that the ground surfaces can be considered locally reacting and that their specific normal impedances can be adequately described by their specific flow resistance (Chessell's model, following Delany and Bazley) we have predicted the spectra of excess attenuation using flow resistance as parameter. Comparing a measured spectrum of excess attenuation with the set of predicted spectra enables one to ascribe an approximate value of specific flow resistance to the ground surface. In this way we find the following ranges of values from both our own and other people's measurements: snow (depends strongly on weather conditions and age), 2 to 20 cgs units; shaded ground in mature forest, 25 to 50; plowed and freshly disked sandy loam, about 50; many different grass sites in several countries, 150 to 300; settled earth with many weeds (but not as dense as “grass”), about 800 to 1000; limestone chips of ½ to 1‐in. size with open voids, 800 to 2000; hard compacted quarry dust, 1000 to 2000; sandy silt well packed by passage of vehicles, about 1000; concrete or mature asphalt, about 20 000 and perhaps greater.
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Environmental noise in Kentucky (A)

A. B. Broderson, W. S. Coakley, R. G. Edwards, T. Jackson, and W. P. Hauser

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S63-S63 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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A state‐wide study was conducted pursuant to development of a Kentucky environmental noise regulation, including assessments of noise and attitudes in 20 cities and impacts of regulation on three mineral processing industries. Urban Leq (daytime mean = 59.1 dBA, sigma = 7.4 dBA; nighttime 5.5 dBA lower) was sufficient for significant noise annoyance and a small potential for permanent hearing loss, judged by EPA “Levels Document” Criteria. Surface transportation was responsible for 80% of the intrusive events and 67% of the high annoyance ratings. Citizens considered urban noise sufficiently harmful to outdoor activity, sleep, and communication to warrant regulation but preferred local over state or federal control and fines for revenues over taxes. An estimated 39% of the coal, rock, and asphalt plants in the state (responsible for most of the complaints to state officials) would violate a 63 dBA test limit; engineering control would cost $10.9 million, rising or falling exponentially with the enforcement limit selected. A proposed regulation is now being finalized. [Work supported by the State of Kentucky.]
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Accuracy of a series of ambient noise measurements (A)

D. A. Driscoll and W. J. Webster

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S63-S64 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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It has been shown that a single 15‐min or 1‐h measurement sequence is a very poor representation of the long‐term ambient noise at a measuring location, even though the data may be a highly accurate representation of the noise during the sample period. For any particular short‐term statistic (e.g., 15 min, Leq, L10, etc.) there is little chance of being within ±3 dB of the corresponding long‐term statistic (based on a month or more of data); ±3 dB limits can be claimed with only 25%–50% confidence depending on the long‐term variability of the noise at the site. However, by taking the composite of several independent 15‐min measurements, ±3 dB accuracy can be claimed with substantially improved confidence. At a suburban site, for example, five measurements will give 70% confidence, seven will give 80% and ten will give 90% confidence. This and similar information for urban and rural sites was derived using Student's t distribution and evaluated experimentally using 100 ways of data from a rural site, 40 days from a suburban site and 60 days from a quiet urban site.
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Environmental noise assessment using short‐term equivalent levels (A)

D. E. Commins and J.‐P. Sirieys

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S64-S64 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Several research projects have been conducted to investigate the possibilities which the A‐weighted energy equivalent level offers, when assessed over short successive periods of time, to set an objective method for the assessment of aircraft, railway, and highway noise, when considered alone or when compounded. Two main aspects have been developed. From a methodological standpoint, the measurement of Leq over short durations, typically 10–60 s, by reducing the amount of stored data, makes it possible to preserve information on the temporal evolution of an environment and thereby to enrich considerably the interpretation of analytical results. Also, from the basic measures, on can calculate Leq over large periods and have then access to different scales of analysis. From an analytical standpoint, “short Leq's” histograms provide an efficient visualization of noise conditions and make it possible, through adjustments of the time basis, to assess the specific contributions of a group or of a type of sources to the overall environment. In the case of single events, short Leq's are good estimates of their acoustical energies. Moreover, if simultaneous measurements are performed, one can evaluate the impact of a type of source using correlation coefficients. These encouraging results should lead to further developments: Prediction methods can be imagined which would represent a considerable improvement over those which predict overall quantities. Contemporary technology is able to provide very convenient devices towards the measurements of “short Leq's.” Prediction and measurement schemes should result into an overall methodology for the objective description of an environment based upon a simple measure whose accuracy could be adjusted according to the nature of the problem at hand. [Under the sponsorship of the Ministry of Environment, Paris, and of the Transportation Research Institute, Bron, France.]
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Vibration and noise prediction of internal combustion engine based on cascade modeling of components (A)

A. Ordubadi, R. Lyon, and R. DeJong

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S64-S64 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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In most machinery noise and vibration problems, a model of the machine as a cascade of subsystems excited by the noise (vibration) source(s) may be used in predicting the effect of any modification in the source(s) or vibration transmission paths. In this study, an acoustic‐dynamic model of an internal combustion engine is developed. The excitation sources considered were combustion forces and piston slap. For combustion forces, two transmission paths from each cylinder to the engine block were considered; a path through the piston, crank shaft and bearings [R. DeJong, 1976] and another path through the cylinder head. The piston slap was assumed to be transferred to the block through the cylinder wall and upper deck of the cylinder block [T. Oguchi, 1979]. The combustion forces of each cylinder were determined from the engine design and its operating conditions. The piston slap excitation was estimated on the basis of the shape and size of the piston and cylinder and assumed to occur after the combustion. The block vibration and the radiated sound power spectrum of a four cylinder in‐line diesel engine were predicted and measured under different operating conditions. The predicted and measured results agreed well above 400 Hz.
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Motorboat noise and technology assessment (A)

J. I. Smullin

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S64-S64 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Motorboat noise, both onboard and remote, from operating motorboats is examined, including standardized procedures for noise measurements, a data base of noise levels from over 500 motorboats, the available technology for engineering noise control techniques, and existing legislation effecting noise emissions from motorboats. In order to support a motorboat noise impact assessment a relationship between full power noise levels, as measured in legislated and engineering society procedures, and partial throttle operation which is representative of the majority of motorboat usage has been determined for each of several categories of motorboats. It is shown that the variance of horsepower weighted noise increases as the responsibility for the propulsion package engineering and manufacturing process for single boat type becomes more widely distributed. Thus the outboard motors show a minimum variance and conventional inboard motorboats show the widest variance. Existing technology for noise control is shown to be effective for reducing noise from presently achieved levels. But, it is shown that hull water interaction noise does create a lower limit of noise, limiting the noise reductions achievable by treatment of motor noise. [Work supported by EPA/ONAC.]
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Noise impact assessment of motorboats (A)

P. J. Wright

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S64-S64 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Motorboating in the U.S. has shown a steady growth over the past two decades to the point where Americans own an estimated 8 500 000 motorboats. The potential impact on the health and welfare of the American population is great. In order to assess this impact, an analytic noise impact assessment model was developed and evaluated. Criteria for impact consist of hearing loss, indoor and outdoor speech interference, and overall annoyance. The model is statistical in nature. Data on source emission levels by motorboat category, source operating characteristics, and usage patterns are combined with transmission path characteristics and population density information relative to source location to generate the statistical distribution of population vs noise level. Different scenarios of contribution of motorboat noise to the A‐weighted energy‐equivalent day—night sound pressure level as well as the effects of single‐event passbys are considered. The methodology for impact assessment is consistent with EPA's benefit assessment procedure. [Work supported by EPA/ONAC.]
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The contribution from propeller cavitation to the airborne noise in after spaces on high speed marine vessels (A)

Leslie M. Gray

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S64-S65 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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Propeller cavitation is often overlooked as a source of airborne noise on ships, because it is unusual to have manned spaces in the vicinity of the propellers. However, when design considerations require that berthing spaces be located over the propellers, cavitation can produce severe airborne and structureborne noise problems. These problems are especially severe in high speed or high power craft, where the propellers are heavily cavitating and the vessel structure is fairly light. This paper presents the results of measurements aboard a high speed (35 knots) research vessel which identifies the contribution to structural vibration and airborne noise from propeller cavitation. Predictions of the airborne noise existing in a proposed crew living space on a similar vessel show airborne noise levels to be 25 dB in excess of compartment specs at a similar speed. The mechanism of propeller cavitation and procedures to estimate source strength are reviewed. Relationships are presented to describe the power input to the hull structure from this source, and to describe the airborne sound power resulting from this hull vibration. Procedures for the control of propeller generated airborne noise are outlined, along with some of the unsolved technical problems associated with each of these noise control procedures.
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Propagation of aircraft ground run‐up noise including the effects of a barrier (A)

C. I. Chessell

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S65-S65 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Measurements of noise levels generated by an F‐111 aircraft during ground run‐ups with after‐burner are reported. The measurements were made at various azimuths and at ranges out to 2.9 km over open ground and also with the aircraft located behind a 4‐m high earth wall. Prevailing meteorological conditions were light winds with both temperature lapse and inversion conditions. The measured noise levels are compared with theoretical model predictions which include the effects of a finite impedance ground, of the meteorological conditions and of the barrier, using the methods of Maekawa [Appl. Acoust. 1, 157–173 (1968)] and Jonasson [J. Sound Vib. 22, 113–126 (1972)] to obtain the diffracted field over the barrier. It is shown that the ground attenuation can be significant out to long ranges but that it may be reduced in part by refraction during downwind propagation. The effects of the barrier are shown to be strong at short ranges but to be negligible at long ranges.
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Motorcycle noise control through use of a stationary sound level test (A)

John B. Walsh and Wayne E. Marcus

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S65-S65 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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New motorcycles have gotten significantly quieter throughout the 1970's. Motorcycle noise control is now a problem of keeping the quiet motorcycles quiet. This problem involves control of both after‐market motorcycle exhaust systems and user modifications of stock exhaust systems. Various stationary sound level tests have been suggested as a means of ensuring that motorcycle exhaust systems are quiet when built, and remain quiet in use. Sophisticated test methods have been proposed, but suffer because of their complexity; simpler tests, however, have lower correlation than the complex test methods. A new approach to the use of simple stationary sound level tests was evaluated, and produced promising results.
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Effectiveness of cylindrically topped noise barriers (A)

S. I. Hayek, J. M. Lawther, and R. P. Kendig

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S65-S65 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Noise barriers having a cross section of a wedge with a cylindrical top is taken as a model for highway berms. These berms are usually covered by vegetation which can be modeled as an absorptive surface. In this study, the noise reduction effectiveness of such noise barriers is assessed as a function of many of the parameters; such as its geometric shape and its acoustic characteristics. The curvature of the cylinder, the interior wedge angle of the sides of the barrier, the acoustic impedance of the barrier's coverage and the location of the highway traffic line from the berm were found to influence the excess attenuation of such a barrier. As the distance between the highway traffic line and the barrier becomes wider, the excess attenuation of the barrier decreases. Similarly, as the curvature of the berm become larger, the excess attenuation increases. The absorptivity of the berm, as modeled by its acoustic impedance, increases the excess attenuation as the berm becomes more absorptive. [Work supported by the National Cooperative Highway Research Program.]
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A ray model for predicting sound attenuation by double barriers (A)

P. C. Fano

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S65-S65 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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The results of J. Keller's Geometrical Theory of Diffraction and A. Pierce's single and double edge diffraction theories are used to develop a theoretical ray model for predicting noise attenuations by double barriers. Acoustical scale model experiments were conducted to test the validity of the theory. The experimental results are compared with the attenuations calculated using a computer model. It is shown that the double barrier attenuation (above and beyond that due to geometrical spreading) should be calculated by cascading the attenuation caused by each of the two barriers. This contradicts the generally accepted assumption that given two widely spaced barriers located between a source and receiver, only one of them significantly reduces the noise reaching the receiver. [Work supported by NSF and MIT; thesis advisor: Prof. Richard H. Lyon.]
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Transmission loss of a steel noise barrier coated with vibration damping material (A)

A. Behar and D. N. May

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S65-S65 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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This is a study into a more economical way of obtaining the required structural sound transmission loss (TL) in steel highway noise barriers by using vibration damping material. When a layer of a high inherent damping is applied to a relatively lightly damped panel, the result is a composite panel with higher damping than the original one. The resulting TL is higher, even below the critical frequency, than that of a single lightly damped panel of the same weight. Adding vibration damping material to a steel barrier improved the Sound Transmission Class (STC) by 3, for only a 20% increase in weight, whereas about a 50% increase in weight would have been required to increase the STC by the same amount through the addition of more steel. The cost of damping material is also lower than of steel, and its use can provide savings of up to about 20% in the cost of noise barrier panels.
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An analysis of traffic noise abatement scenarios (A)

G. W. Cermak, C. R. von Buseck, and R. D. Blanchard

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S65-S66 (1979); (2 pages)

Online Publication Date: 11 Aug 2005

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Computer simulations of traffic sound levels were performed to evaluate the probable effectiveness of several hypothetical noise abatement scenarios in reducing residential exposure to traffic sound. These simulations were performed for 28 actual census tracts in six cities which were chosen to be representative of the urban United States. Results showed that neighborhood land use patterns have a strong influence on residential traffic noise exposure and thus constrain the potential effectiveness of any noise abatement strategy. Limits on the acceleration noise of new automobiles were calculated to have only a small effect on traffic noise exposure, while limits on truck acceleration noise were calculated to have a greater effect. A combination of noise barriers along freeways and nonresidential zoning along arterials was calculated to have approximately the same effect on residential noise exposure as severe constraints on both automobile and truck acceleration noise levels. Further calculations showed that if no constraints on new vehicle noise levels were imposed, and if the new vehicle fleet included more four cylinder and diesel automobiles, residential traffic noise exposure would be marginally greater than at present.
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Vehicle directionality and propagation characteristics as errors in traffic noise predictions (A)

John S. Bradley

J. Acoust. Soc. Am. Volume 65, Issue S1, pp. S66-S66 (1979); (1 page)

Online Publication Date: 11 Aug 2005

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Several traffic noise prediction equations assume vehicles act as point sources, and radiate sound spherically. The energy average sound level (Leq) is then obtained by integrating over the passby of such a source. Measured vehicle passby sound levels under controlled conditions and at a number of microphone locations, for both grass and asphalt covered ground indicate considerable deviations from these assumptions. More complex models are considered and the resulting reductions in Leq errors are presented. Computer calculations using more exact propagation theory for grass and asphalt covered ground indicate further errors in Leq predictions can occur. The magnitude of the errors depend on the source spectrum and microphone location.
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