Showing papers on "Noise pollution published in 1982"

Community annoyance from aircraft and ground vehicle noise

Abstract: Data from published noise‐annoyance surveys are related to a common measure of noise exposure Ldn. The results provide means for predicting the annoyance (experienced by percentages of people of normal and of supersensitivity) attributable to noise from aircraft and from street and road traffic. Correlations of 0.90 to 0.95 are found between Ldn and percentages of people annoyed by aircraft noise when low, moderate, and higher levels of annoyance are measured for both a broad range (35 dB) and a restricted range (20 dB) of Ldn. Noise from urban street and road traffic is shown to cause less annoyance than the noise from aircrafts when both have the same Ldn as typically measured or estimated for outdoors. The difference, equivalent to a difference of about 10 dB in Ldn, is attributed to acoustical factors that diminish in‐and‐around‐the‐home noise dosages from ground vehicular traffic compared to dosages from aircraft operations. Generalized functions showing degrees of annoyance and percentages of U.S. u...

Effects of Aircraft Noise on Reading Ability of School–Age Children

Abstract: The percent of students reading below grade level from 1972 to 1976 was regressed on racial, socioeconomic, educational, and noise level variables for all elementary schools in Brooklyn and Queens, New York. Schools were assigned noise exposure scores based on Noise Exposure Forecast contours for New York City airports. The correlations between these noise scores and a variety of noise level metrics ranged from 0.74 to 0.97. The regression coefficients adjusted for confounding factors, indicated that an additional 3.6% of the students in the noisiest schools read at least 1 yr below grade level with 95% confidence limits from 1.5 to 5.8%. The dose-response relationship indicated that the percent reading below grade level increased as noise level increased.

Spectral analysis of impulse noise for hearing conservation purposes

Abstract: Damage-risk criteria for impulse noise does not presently take the spectrum of the impulse into account; however, it is known that the human auditory system is spectrally tuned. The present paper advocates the extension to impulse noise of the noise dose concept which is widely used for continuous noise. This approach is based upon sound exposure instead of sound pressure. An A-weighting filter or an octave band analysis can then be used to take the spectral content of the impulses into account. The equipment needed for applying these procedures for impulse noise is an integrating sound level meter or a digital Fourier processor. Generalized spectral methods have been evaluated by means of an impulse simulation applied to a mathematical model of the human hearing mechanism. The results of this simulation agree with the most recent experiments on impulse noise and fully support the proposed rating methods. This conclusion must be emphasized as it leads the derivation of a uniform procedure for predicting loudness and damage risk for hearing which is applicable for continuous noise as well as for impulse noise.

An iterative method for predicting turbofan inlet acoustics

Abstract: A new iterative solution technique for predicting the sound field radiated from a turbofan inlet is presented. The sound field is divided into two regions; the sound field within the inlet which is computed using the finite element method and the radiation field outside the inlet which is calculated using an integral solution technique. A "unified" solution is obtained by matching the finite element and integral solutions at the interface between the interior and exterior regions. The applicability of the iterative technique is demonstrated by considering several simple cases for which exact or *'classical" solutions for the sound field are available. These examples show that the proper solution is obtained within five iterations. The overall accuracy of the method is demon- strated by comparison with experimental data. ROWING concern in recent years over the rise in noise pollution, especially that caused by turbofan engines, has created considerable interest in developing methods for predicting the acoustic properties for these engines. The two major sources of turbofan engine noise are the externally generated noise produced by the jet exhaust and the internally generated noise due to the rotating turbomachinery, turbofan blades, and combustion processes. The noise due to jet exhaust has become less intense due to the use of high bypass ratio turbofan engines which have a reduced jet velocity over earlier low bypass ratio engines. This, in turn, has made the noise produced by the turbofan more apparent. In an attempt to reduce the turbofan noise, much effort has been expended in the development of acoustic liners for these engine inlets. Unfortunately, due to the lack of analytical methods for such development, most of the design work for these liners has been performed by costly cut and try methods. For this reason, analytical methods are needed to equip the designer with the tools necessary for the job of designing quieter ef- ficient turbofan inlets. As the first step in a theoretical approach to reducing the amount of noise that will reach an observer, whether it be a passenger in the aircraft or an observer on the ground, an analytical procedure for predicting the acoustic field of the engine must be developed. This analysis should include the effects produced by short inlet ducts with varying geometry and lined inlet walls. To date, no such analytical method for predicting the entire sound field exists. This paper describes a general approach for calculating the acoustic field of a tur- bofan inlet. The approach is not restricted to any particular computational schemes. Thus, many of the analytical ap- proaches presently used in duct acoustics can be extended to provide a realistic description of the entire sound field. Consider the somewhat idealized inlet shown in Fig. 1. Noise produced within the engine propagates down the inlet duct and radiates out to the surrounding environment. The

Noise at work--tolerable limits and medical control.

Abstract: An attempt is made to assign TLV's to noise in a manner similar to that used by the ACGIH for chemical substances Based on these criteria and available data, it would appear that the TLV-TWA for noise should be less than 65 dBA Since it is unlikely that this limit will be accepted at any time in the near future, another approach is necessary It is suggested that the expected degree of social hearing impairment at age 70–75 be used as the control criteria To establish a connection between hearing-loss and social hearing impairment, exposure data developed by Passchier-Vermeer and Robinson were correlated with presbycusis data reported by Spoor for the period following exposure It can be shown that, even with a limit of 80 dBA, noise induced social hearing impairment among the elderly could be expected in 10% of the population It should be the function of the Occupational Health Services to identify these people by means of audiometric testing

Automatic Identification of Noise Pollution Sources

Abstract: Instrumentation currently available for the automatic monitoring of noise nuisance has the shortcoming that although the intensity, duration, and time of occurrence of noises may be recorded, their source often cannot be identified. Research directed towards providing improved instrumentation which can identify sound sources is described. Our results suggest that application of statistical pattern recognition to recorded sounds can differentiate sources which are structurally dissimilar (e.g. trains, fixed-wing aircraft, helicopters) with an accuracy of better than 95 percent. The work is continuing to discriminate sounds which are structurally similar (e.g. different types of aircraft), and to produce hardware capable of field application.

We have just begun to create efficient transport aircraft

Abstract: Factors affecting the cost-effectiveness and economics of the air transportation industry are reviewed. The delivery of more fuel-efficient aircraft and eventual total replacement in the 1990's by fleets of advanced aircraft are seen to offset rising fuel costs. Better airport operations are perceived to eliminate fuel-costly delays due to overcrowded runways, lack of available carriers, and maintenance of aircraft in holding patterns. Noise reduction research will lower the lawsuit costs from noise pollution, and the introduction of advanced turbofans for long, short, and medium range flights, advanced commuter planes, and advanced SSTs offering projected 50% increases in current aircraft efficiencies are seen to be limited only by the airlines' ability to provide purchase financing, rather than by a lack of available new technology.

Warning noise generator

Abstract: It is intended to be ensured that a warning noise generator is always heard, even when a high noise level prevails at a workplace. On the other hand, unnecessary noise pollution is intended to be prevented. An automatic, noise-level dependent volume control is therefore provided. A loudspeaker (10) serves as a warning noise generator. The noise level is monitored by a microphone (16). The signals fed to the loudspeaker (10) are simultaneously connected as feedback to an amplifier (18) for the microphone signals.

Predictions of low-frequency sound from the MOD-1 wind turbine

Abstract: The purpose of this project was to determine if aerodynamic noise mechanisms are associated with the acoustic noise situation that results from the operation of the MOD-1 wind turbine near Boone, NC. Acoustic measurements indicate that sound from the turbine produced structural vibrations in homes near the turbine site. The possible sources of aeroacoustic noise studied were steady blade loads, unsteady blade loads due to wind shear, and unsteady loads on the blades as they pass through the tower wake. Mathematical models that were used to study these noise sources are described. The results showed that the most significant source of impulsive, low-frequency sound was the unsteady loads that occurred when the blade passed through the tower wake. This problem might be resolved by operating the turbine at a lower rotor speed. This issue might also be resolved by changing the structural configuration of the tower to create an azimuthally smoother wake which would dramatically reduce the noise.

Noise control techniques for the design of coal preparation plants. Open file report Jun 80-Sep 82

Abstract: The purpose of this work was to document the currently available noise control techniques that can be incorporated into new coal preparation plants during the design stage. This was accomplished by reviewing previous experience, conducting an extensive literature search, visiting operating coal preparation plants, and contacting various equipment manufacturers. The treatments addressed include equipment substitution, changes in plant layout, and retrofit treatments for existing equipment.

Evaluation of noise control technology and alternative noise certification procedures for propeller-driven small airplanes

Abstract: : This report considers the effectiveness of current noise regulations in Appendix F of FAR Part 36, examines the potential effectiveness of future technology to achieve further noise reduction, and evaluates a number of new concepts for noise certification procedures for propeller-driven small aircraft. The latter were based, in part, on results of a flight test program carried out with Cessna Aircraft Company, to evaluate the utility of takeoff noise tests and the possible use of sound exposure level as a suitable metric for noise certification of the subject aircraft. The study indicates that existing regulations have been effective in stimulating development of quieter propellers for the existing fleet of propeller-driven small aircraft. However, it does not appear economically feasible to achieve more noise reduction in most of this fleet using existing technology with the possible exceptions of some of the two-engine aircraft. However, application of future noise reduction technology, primarily for quieter propellers, should allow a reduction in current noise limits by about 6 dB and should reduce levels of the noisiest aircraft in the current fleet by as much as 10 dB. A takeoff test is appropriate for all propeller aircraft except those equipped with cruise-optimized fixed-pitch propellers. For this test, the current level flyover test appears to represent the noisiest operating condition.

Standards against noise pollution: the case of Shinkansen trains in Japan

Abstract: This paper analyzes the noise pollution problem of high-speed trains (Shinkansens) in Japan. A decision analytic approach is used to structure the problem and to identify sources of conflict among the actors involved in railway noise standard setting. The Shinkansen noise pollution problem is characterized by the inherent inequity of the risk-benefit distribution resulting from the train operations. While the benefits of high-speed transportation are shared by many travellers, the burden of the noise impact is carried by relatively few residents. This conflict is institutionally expressed in the opposing values of the Japanese National Railway and the Nagoya Association against Shinkansen Pollution. In attempting to resolve the conflict, the Environment Agency of Japan set noise pollution standards of 70-75 dB(A). The Japanese National Railway argued for less stringent standards because of economic, speed, and service objectives. Resident organizations, in contrast, requested more stringent standards because of psychological and health impacts. However, both arguments appear to have influenced the final standard only indirectly. Instead, standards were set mainly on the basis of noise-complaint relationships and on the basis of consistency with existing noise standards.

Helicopter Noise Exposure Curves for Use in Environmental Impact Assessment.

Abstract: : This report establishes the current (1982) FAA helicopter noise data base for use in environmental impact assessment. The report sets out assumptions, methodologies, and techniques used in arriving at noise-exposure-versus-distance relationships. Noise data are provided for 15 helicopters, including five flight regimes each: takeoff, approach, level flyover, hover in-ground-effect (HIGE) and hover out-of-ground effect (HOGE). When possible, level flyover data are presented for a variety of airspeeds. Sound exposure level (SEL) is provided for all operational modes except hover. In the case of hover operations (both HOGE and HIGE), the maximum A-Weighted Sound Level (LAM) is identified as a function of distance. The report also includes a discussion of helicopter performance characteristics required for full computer modeling of helicopter/heliport noise exposure. (Author)

Noise and economic characteristics of an advanced blended supersonic transport concept

Abstract: Noise and economic characteristics were obtained for an advanced supersonic transport concept that utilized wing body blending, a double bypass variable cycle engine, superplastically formed and diffusion bonded titanium in both the primary and secondary structures, and an alternative interior arrangement that provides increased seating capacity. The configuration has a cruise Mach number of 2.62, provisions for 290 passengers, a mission range of 8.19 Mm (4423 n.mi.), and an average operating cruise lift drag ratio of 9.23. Advanced operating procedures, which have the potential to reduce airport community noise, were explored by using a simulator. Traded jet noise levels of 105.7 and 103.4 EPNdB were obtained by using standard and advanced takeoff operational procedures, respectively. A new method for predicting lateral attenuation was utilized in obtaining these jet noise levels.

FAA Integrated Noise Model Validation: Analysis of Air Carrier Flyovers at Seattle-Tacoma Airport,

Abstract: : The Federal Aviation Administration's Integrated Noise Model (INM) is a series of computer programs designed to estimate environmental noise levels in the vicinity of an airport. As part of the effort's to validate INM outputs for the FAA, comparisons were made between the Sound Exposure Levels (SEL) of actual aircraft flyovers at Seattle-Tacoma International Airport and SELs which were computed by the INM for identical conditions. Data for this analysis were obtained from the FAA ARTS-III radar to determine the actual slant range and velocity of observed aircraft, and from noise monitors located beyond each runway end to determine actual SEL values associated with observed aircraft. The report presents the results of the comparison of INM and observed SEL values for seven transport-category aircraft.

Comparison of aircraft and ground vehicle noise levels in front and backyards of residences

Abstract: Investigation of aircraft overflight and ground vehicle noise around a general aviation airport provided the opportunity to measure the frontyard to backyard noise reduction afforded by residential structures for these two types of noise sources. The measured average noise reduction for two residences using passing street vehicles as noise sources was found to be 17 and 21 dBA. For aircraft overflights using identical measurement instrumentation and microphone locations, as were used for the street traffic noise, the average measured noise reduction (i.e., difference between frontyard and backyard noise levels) was found to be 0.2 and 0.4 dBA. The results of the measurements show that acoustical factors around residences are such as to generally cause substantial frontyard to backyard noise reduction for street traffic noise, but not for the noise from aircraft overflights.

A study of general aviation community noise impact and annoyance

Abstract: The method involved the selection of three airports which were dominated by aircraft weighing 12,500 lbs or under and which were also undergoing a change relative to utilization. Also, there was interest in airports with different utilization levels so that effect of number of operations could be considered. In addition, there was a requirement to select airports with communities in the surrounding areas which were exposed to aircraft operations noise. Noise annoyance response data was obtained from available sources. These sources included environmental impact statements, interviews with airport managers, noise complaint information, community meetings concerned with projected changes in airport utilization, and social survey data. As a means of objectively assessing the noise impact due to aircraft operations, noise measurement and computer noise modeling determinations were obtained for each airport. Listening quality tape recordings were also obtained.

Far-field acoustic data for the Texas ASE, Inc. hush house

Abstract: Abstract : This report supplements AFAMRL-TR-73-110, which describes the data base (NOISEFILE) used in the computer program (NOISEMAP) to predict the community noise exposure resulting from military aircraft operations. The results of field test measurements to define the single-event noise produced on the ground by military aircraft/engines operating in the Texas ASE Inc. hush-house are presented as a function of angle (0 to 180 from the front of the hush-house) and distance (200 ft to 2500 ft) in various acoustic metrics.