Showing papers on "Noise pollution published in 1992"

Noise exposure, noise annoyance and their relation to psychological distress, accident and sickness absence among blue-collar workers--the Cordis Study.

Abstract: This study examined the impact of chronic industrial noise exposure on psychological distress symptoms, accident involvement and sickness absence among male and female workers. It also examined whether workers expressing high noise annoyance were more adversely affected by it. Subjects were blue-collar workers, 1,680 males and 688 females, who participated in the Cordis Study. Noise exposure levels were: low [ or = 85 dB(A)]. For males, noise exposure level affected job dissatisfaction and post-work irritability, while for females it also intensified somatic complaints, anxiety and depression. All the distress symptoms were higher for females. Further analysis showed that the significant increase of symptoms with noise exposure level was only for workers reporting high annoyance. Higher noise exposure levels were associated with increased accidents and sickness absence for both sexes. Noise-annoyed males had a significantly higher percentage of accidents when exposed to moderate noise levels and a marked increase in sick leave at high noise levels. Finally, the nonauditory effects studied here were already prevalent at moderate noise exposure levels, especially among noise-annoyed workers. This indicates the importance of reducing even moderately high levels of industrial noise not usually considered harmful to hearing.

Noise: breaking the silence.

Abstract: Many patients produce their own femorofemoral collaterals (note the suprapubic varicose veins). Operation in such patients is unnecessary. There are no reliable and safe methods for repairing incompetent valves in deep veins. Research continues, however, and includes assessment of transplanting vein valves from the axillary vein into the upper popliteal segment. This has relieved symptoms in some patients, and calfpump function has been improved. Additional attempts have been made to repair femoral vein valves. This may have a place in patients with congenital valve aplasia, but so far there has been no long term follow up in patients who have undergone repair of valves after thrombosis in limbs. The support of incompetent valves with external slings has also been tried, with encouraging initial results. Longstanding venous occlusion may be treated by bypass. The contralateral normal long saphenous vein is dissected out and anastomosed to the femoral vein on the occluded side. The iliac occlusion is bypassed and encouraging results have been obtained. The adjunctive use of a temporary arteriovenous fistula increases flow, and this maintains patency. Bypass of an occluded superficial femoral vein (using long saphenous vein) does not give equally good results. Synthetic materials are rarely used in the venous system except as simple patches, but externally reinforced polytetrafluoroethylene is the material of choice for replacement of the iliac veins and the inferior vena cava.

Noise pollution in the operating room: a hazard to surgeons, personnel and patients

Abstract: Noise levels up to 118 dB--a level that is potentially damaging to the hearing--were measured in the operating room, notably during the use of high-speed gas turbine bone-cutting drills. Suction tips, which had trapped tissue "whistles" inside, yielded noise levels of up to 96 dB. Surgeons, staff, and patients should be cautioned against such noises and shielded in prolonged cases. We offer a review of acoustical criteria for various practical noises and duration of safe exposure.

Effect of Personal and Situational Variables on Noise Annoyance: with Special Reference to Implications for En Route Noise

Abstract: Over 680 publications from 282 social surveys of residents' reactions to environmental noise have been examined to locate 495 published findings on 26 topics concerning non-noise explanations for residents' reactions to environmental noise This report (1) tabulates the evidence on the 26 response topics, (2) identifies the 495 findings, and (3) discusses the implications for en route noise assessment After controlling for noise level, over half of the social survey evidence indicates that noise annoyance is not strongly affected by any of the nine demographic variables examined (age, sex, social status, income, education, homeownership, type of dwelling, length of residence, or receipt of benefits from the noise source), but is positively associated with each of the five attitudinal variables examined (a fear of danger from the noise source, a sensitivity towards noise generally, the belief that the authorities can control the noise, the awareness of non-noise impacts of the source, and the belief that the noise source is not important)

Noise in multiple-workstation open-plan computer rooms: measurements and annoyance.

Abstract: Computers in the workplace have become very prevalent. As with the introduction of any new technology, unanticipated problems often develop. Noise in open-plan computer rooms and annoyance and perceived deterioration in performance associated with it also appears to be a problem that may be similarly categorized. An experimental investigation was undertaken as a result of frequent user complaints about the difficulty of concentrating and performing their work in the computer rooms of a large service organization. Two typical computer rooms were investigated. Noise levels were measured at random times during the working hours. The noise spectrum was found to be almost similar in both facilities. The 10-second A-weighted noise level for all frequencies ranged between 53 and 62 dB. Most noise energy was either in the high-frequency bands (above 2,000 Hz) or low-frequency bands (below 500 Hz). The highest noise energy levels were recorded at 8,000 Hz (between 64 and 73 dB). Least noise energy levels were recorded between 500 and 2,000 Hz (between 35 and 44 dB). The noise spectrum, thus, was substantially different from those of open-plan offices. Eighty-nine percent of the users questioned indicated their tasks required concentration. Fifty percent of all respondents rated the noise level between extremely annoying and unbearable and intolerable (scale values between 22 and 25 on a 25-point scale; 1 being noticeable but not objectionable and 25 being unbearable and intolerable); 10% of the respondents considered the noise very annoying; 20% of the respondents considered the noise levels moderately annoying; the remaining respondents did not seem to have a major problem. Conversational sound and computer-printer beeping sounds were reported to be most annoying by 90% of the respondents who considered the noise levels annoying. Constant arrival and departure of users, sound from keyboards, and ventilation equipment also appeared to be major contributing factors.

Aircraft noise annoyance and average versus maximum noise levels.

Abstract: A questionnaire study was performed in seven areas located around the airports of Landvetter and Save, Gothenburg, in an attempt to elucidate the extent of annoyance in populations exposed to aircraft noise. Noise exposure was estimated as the energy equivalent level (Aircraft Noise Level—FBN) or as the number of aircraft with levels that exceeded 70 dBA, combined with the maximum noise level. The results were compared with data obtained from the earlier Scandinavian Aircraft Noise Investigation. The results supported the conclusion that the annoyance reaction is better related to the number of aircraft and the maximum noise level than to energy equivalent levels for noise exposure.

The dormant Noise Control Act and options to abate noise pollution.

Abstract: In 1981, Congress ended funding for the Office of Noise Abatement and Control (ONAC) at the Environmental Protection Agency (EPA). Before the elimination of ONAC, EPA engaged in a wide variety of activities to abate noise pollution under the authority of the Noise Control Act and, after 1978, the Quiet Communities Act. Elimination of ONAC’s funding has stymied noise abatement efforts at both the federal and state level, while noise levels have probably increased. Without federal action, little governmental noise abatement activity can be expected. Although Congress has several options to abate noise pollution, funding EPA to implement the NCA is the best solution.

Noise exposure level while operating electronic arcade games as a leisure time activity.

Abstract: In order to study noise levels associated with electronic arcade games, noise measurements were made in 3 selected game centers and 192 samples were taken in each location. The background noise was recorded at a level of 61 dB(A) and 64 dB(C). When the electronic games were performed these levels of noise reached to 88 approximately 90 dB(A). The 1/3 octave bands analyzing sound pressure levels showed that more intense noise levels arose in a frequency range between 0.5 and 2.0 kHz. The computed values for noise pollution levels (LNP) and L90 (fast response A-weighted sound level exceeded 90% of the measurement time) ranged from 93.3 to 96.6 and from 85.1 to 87.3 dB(A), respectively. Concerning our results and according to Melnic (1979), it was estimated that these levels of noise might cause 4-8 dB temporary threshold shift (TTS) at 4.0 kHz in an individual with less than one hour of exposure to such a level of noise. As for the employees of the 3 game centers, the 8-hr equivalent continuous sound levels (Leq,8) were in the range of 80.3 approximately 87.5 dB(A), although their exposure time could not be exactly determined. It was suggested that: 1) The maximum levels should be limited to a reasonable level, either by the manufacturers or by the game center owners; 2) Education programs in industry should inform the employees about other factors outside the work that may affect their hearing; and 3) For policy-making on hearing conservation, recreational warning and standards should be established.

Noise Measurement and Numerical Simulation of Oil Flow in Pressure Control Valves.

Abstract: The recent development of a highly pressuriezed oil-hydraulic system poses serious problems of environmental pollution such as noise pollution, vibration hazards and so on. Hydraulic valves may frequently be a source of noise, especially cavitation noise. In this paper, we have carried out both noise tests and numerical simulations of oil flows on various configurations of the electroproportional relief-flow control valves, and set up some design criteria for the low noise valves by comparison of measured and computed results. In particular, we discuss and clarify the effects of the volume of a valve chamber, a two-stage restrictor, angles of a poppet and a valve seat, and the overlapping distance on a poppet.

Impact of Road Traffic and Other Sources of Noise on the School Environment

Abstract: The scale of traffic noise problems and its impact on the indoor environment of schools were investigated in 105 of 351 schools in Singapore. The assess ment of traffic noise was made objectively, and its impact on the background noise levels in schools was evaluated, using speech intelligibility tests and a subjective survey. The results showed a significant reduction in speech intelli gibility when the background noise was raised from 55 to 65 dBA. Methods of effecting noise control in class-rooms have been investigated, from which it was shown that noise reduction of up to 6 dBA can be achieved without major changes to the architectural design and cost. Thus road traffic noise has a significant impact on the acoustical performance of schools in cities with a high population density, especially those situated in hot and humid climatic zones, where natural ventilation is essential for thermal comfort.

The Potential for Mitigation of Gun Blast Noise through Sheltering of the Source

Abstract: : Community reaction to noise from guns of various sizes is a continuing problem for Army training facilities. While the higher-frequency components of gun noise are substantially attenuated by the atmosphere, the low frequency components are often strong enough to cause annoyance or alarm in the surrounding community. It is desirable for training range managers to mitigate noise as much as possible at the source to avoid violating local noise regulations and risking the loss of training capacity. It has been suggested that a community in a specific direction from a firing point could be shielded significantly from gun noise by an acoustic shelter erected in the immediate vicinity of the gun. This report includes the results of mathematical analyses for two idealized shelter models-one designed to mitigate artillery and tank blast noise, the other to mitigate rifle fire noise. The results suggest that acoustic sheltering of this sort probably would not effectively shield a community from the noise of large guns but may work effectively to mitigate rifle noise.

Noise immunity learning for word-spotting speech recognition

Abstract: This paper discusses noise immunity learning in speech recognition by word-spotting. In the proposed method, the learning speech data with superposed noise is constructed by adding the noise data to the clean speech data collected beforehand. Then the recognition dictionary for word-spotting is trained to improve noise immunity. In the learning, the recognition by word-spotting is attempted for the artificially synthesized learning data while gradually increasing the ratio of the contained noise. The recognition is executed using the learning word feature vector automatically extracted based on the similarity. The noise immunity is realized by the simulation in the noisy environment and the automatic learning. The recognition and learning use the word as the unit and the multiple similarity method, which can cope with a wide range of pattern deformation. An evaluation experiment is executed using 13-word speech data (plus noise in a railway station). For the case of 96-dimensional word feature vector (eight dimensions for frequency and 12 dimensions for time), and S/N ratio of 10 dB, the recognition rate is improved from 85.5 percent in the word-spotting method without learning to 94.1 percent with learning. This indicates the usefulness of the proposed method.

A NASA Lewis comparative propulsion system assessment for the High-Speed Civil Transport

Abstract: The topics covered include the following: High Speed Research (HSR) Propulsion System Studies; HRS System Study flowpath; design point aircraft sizing - no noise constraint; impact of noise constraint; noise impact on aircraft size; takeoff gross weight assessment; impact of High Speed Civil Transport (HSCT) high-altitude flyover noise; HSR NO(x) reduction status; current assessment of HSCT ozone depletion; influence of non-optimum cruise altitude on range; and influence of subsonic leg on range.

Exit noise absorption tunnel

Abstract: PURPOSE:To prevent noise pollution by providing a closed type noise absorption treatment structural part on which noise absorbing materials are sticked at the exit of a runnel, and reducing the diffusion of noise generated at the time when vehicles pass through the exit CONSTITUTION:A porous sintered body 13 or glass wool, foamed body, etc, a honeycomb material 13, a back board 14 are integrally laminated to form a noise absorption treatment structural part-consisting body 11 Then, outside or inside the tunnel exit 4, or over both sides, an enclosed type noise absorption treatment structural part 3 is provided to be lined and fixed with the consisting body 11 Besides, the wall thickness of the structural part 3 may be made to be straight or tapered, and noise absorption structures of expansion type, interference type, resonance type, etc, can be attached to the structural part Noise at the tunnel exit due to the passage of vehicles can thus be reduced, and noise pollution can be reduced by narrowing an equivalent noise area diffusing around the exit Further, this method can be easily applicable to both new and existing tunnels

Noise Barrier Simulated by Rigid Screen with Back Wall

Abstract: The problem related to noise barriers is simulated by a still, single‐frequency, three‐dimensional sound source located within two parallel screens with rigid back walls. The solution of a reflection sound field is represented by an asymptotic solution, which is derived by the method of steepest descent. We find that there is a periodic relationship between the screen‐reflection coefficient and the gap‐to‐wavelength ratio (d/λ) of the noise barrier. And there is another parameter called screen Reynolds number (Re), which regularly affects the value of the screen‐reflection coefficient. The optimum choice of noise barrier that minimizes reflection within parallel noise barriers, according to the numerical results, is Re=1, and d/λ=1/4. We also find that increasing the height of the noise barrier in order to improve its noise‐control effect is not economical.

A methodological approach to urban noise assessment

Abstract: Different procedures have been used to assess noise in environmental sound pollution studies. In this paper, a group of Semantic Differential Scales are proposed, reporting the results obtained with nine of them in a study carried out in four zones of a city, where subjects appraised the urban noise heard at home. The zones had different features with respect to the subjects’ social‐cultural status, activities developed in them and noise levels. The aim of this survey was to find out if Semantic Differential Scales used were suitable for characterizing and differentiating the four zones studied, according to Osgoods’ affective dimensions of meaning: Evaluation, Potency and Activity, including some of the effects produced by noise. Data were analyzed through the use of the Principal Axes Factorial Analysis and Varimax rotation, nine one way ANOVAS and t‐tests based on minimum significant differences. Results showed that the scales were suitable.

Aero acoustic analysis and community noise. HSCT climb to cruise noise assessment

Abstract: The widely accepted industry High Speed Civil Transport (HSCT) design goal for exterior noise is to achieve Federal Aviation Regulation (FAR) Part 36 Stage 3 noise limits currently required for new subsonic aircraft. The three phases of the concern are as follows: (1) airport noise abatement at communities close to the airport, (2) climb power opening-up procedures, and (3) the climb to cruise phase affecting communities far from the airport.

Noise Control Technology With Reference to Natural Gas Compressor Stations Under the Aspect of Investment Costs

Abstract: For the conveyance and storage of natural gas, compressor stations are required where the installed power output varies mostly between 1 MW and 20 MW. The noise control measures involved to meet the environmental noise emission regulations in Europe will be presented. The most economical noise control techniques are described particularly for the intake and exhaust systems of gas turbines, the housing of such engines, and peripheral sound sources like gas coolers, oil coolers, and aboveground piping.

Prediction of noise in industrial workrooms

Abstract: This paper reviews the state of the art of noise (steady‐state sound‐pressure level and reverberation time) prediction in industrial workrooms. First, some experimental results are presented to illustrate typical workroom noise characteristics. The room‐acoustical parameters that must be included in a comprehensive prediction model are discussed. Available theoretical prediction approaches (diffuse‐field theory, method of images, ray tracing, simplified models), with their associated advantages and disadvantages, are reviewed. Ray tracing, the most comprehensive approach, is described in some detail. The results of on‐going work aimed at determining applicable values of the input prediction parameters (surface and furnishing absorption coefficients and furnishing densities) are discussed. The main problems associated with workroom noise prediction are summarized. Finally, two case studies, one involving comparing measured and predicted noise levels in a power generating station and another involving predicting the effectiveness of noise‐control treatments in a workshop, are presented.

Tiltrotor Aircraft Noise: A Summary of the Presentations and Discussions at the 1991 FAA/Georgia Tech Workshop

Abstract: : Georgia Institute of Technology hosted a workshop in Atlanta on 28 and 29 March 1991 on the noise problems associated with tiltrotors. The workshop had two major objectives: (1) to review the status of research and development in predicting and reducing tiltrotor noise; and, (2) to identify key technical and operational issues and methods to address them. The second objective had both near term and far term implications. In the near term, the goal is to arrive at a level of technical credibility that can support decisions to develop urban and inner city markets. I The long term goal is to target resources and actions which will lead to tiltrotor noise abatement and effective control. The opening session of this workshop consisted of an overview and a discussion of the physics of tiltrotor noise mechanisms. A review of the available experimental data followed. A discourse on potential flight operational procedures to minimize noise impacts, and a general presentation of industry and government perspectives concluded the workshop. Subsequent sessions were available ford participants to present observations on and experiences with the XV-15 and V-22. Operational experiences included flight tests, wind tunnel tests, and other simulations. Experiences with computational fluid dynamics codes, small-scale model testing, and other related research were shared. This document provides a summary of the presentations and discussions that took place during the workshop.

Traveling line of linear motor type electric vehicle

Abstract: PURPOSE:To prevent the noise pollution of a traveling line by providing a sound-proof cover, which is made of metal material or nonmetal material having damping effect, in the lower surface of a fixing fitting for laying a reaction plate on a track. CONSTITUTION:A reaction plate 9 is laid between tracks, which is formed with sleepers 7, 7' on a road floor 8, through a fixing fitting 12 to form a traveling line. Next, the electromagnetic force is generated between a linear motor and the reaction plate 9 to obtain the thrust and the attraction force, and while an electromagnetic field and the noise are generated in the reaction plate 9, and the noise echoes in the inner space of the fixing fitting 12. A sound-proof cover 14 made of damping steel plate or the like is provided in the lower surface of the fixing fitting 12 to hinder the noise, and noise transmission to an opening 13 between the sleepers 7, 7' and the road floor 8 is hindered. The noise generated from the traveling line can be thereby reduced.