Showing papers on "Noise pollution published in 2004"

Perception and annoyance due to wind turbine noise : a dose–response relationship

Abstract: Installed global wind power increased by 26% during 2003, with U.S and Europe accounting for 90% of the cumulative capacity. Little is known about wind turbines’ impact on people living in their vicinity. The aims of this study were to evaluate the prevalence of annoyance due to wind turbine noise and to study dose–response relationships. Interrelationships between noise annoyance and sound characteristics, as well as the influence of subjective variables such as attitude and noise sensitivity, were also assessed. A cross-sectional study was performed in Sweden in 2000. Responses were obtained through questionnaires (n=351; response rate 68.4%), and doses were calculated as A-weighted sound pressure levels for each respondent. A statistically significant dose–response relationship was found, showing higher proportion of people reporting perception and annoyance than expected from the present dose–response relationships for transportation noise. The unexpected high proportion of annoyance could be due to visual interference, influencing noise annoyance, as well as the presence of intrusive sound characteristics. The respondents’ attitude to the visual impact of wind turbines on the landscape scenery was found to influence noise annoyance.

External and internal noise surveys of London primary schools.

Abstract: Internal and external noise surveys have been carried out around schools in London, UK, to provide information on typical levels and sources to which children are exposed while at school. Noise levels were measured outside 142 schools, in areas away from flight paths into major airports. Here 86% of the schools surveyed were exposed to noise from road traffic, the average external noise level outside a school being 57 dB L(Aeq). Detailed internal noise surveys have been carried out in 140 classrooms in 16 schools, together with classroom observations. It was found that noise levels inside classrooms depend upon the activities in which the children are engaged, with a difference of 20 dB L(Aeq) between the "quietest" and "noisiest" activities. The average background noise level in classrooms exceeds the level recommended in current standards. The number of children in the classroom was found to affect noise levels. External noise influenced internal noise levels only when children were engaged in the quietest classroom activities. The effects of the age of the school buildings and types of window upon internal noise were examined but results were inconclusive.

Aircraft noise around a large international airport and its impact on general health and medication use

Abstract: Aims: To assess the prevalence of general health status, use of sleep medication, and use of medication for cardiovascular diseases, and to study their relation to aircraft noise exposure. Methods: These health indicators were measured by a cross-sectional survey among 11 812 respondents living within a radius of 25 km around Schiphol airport (Amsterdam). Results: Adjusted odds ratios ranged from 1.02 to 2.34 per 10 dB(A) increase in Lden. The associations were statistically significant for all indicators, except for use of prescribed sleep medication or sedatives and frequent use of this medication. None of the health indicators were associated with aircraft noise exposure during the night, but use of non-prescribed sleep medication or sedatives was associated with aircraft noise exposure during the late evening (OR = 1.72). Vitality related health complaints such as tiredness and headache were associated with aircraft noise, whereas most other physical complaints were not. Odds ratios for the vitality related complaints ranged from 1.16 to 1.47 per 10 dB(A) increase in Lden. A small fraction of the prevalence of poor self rated health (0.13), medication for cardiovascular diseases or increased blood pressure (0.08), and sleep medication or sedatives (0.22) could be attributed to aircraft noise. Although the attributable fraction was highest in the governmentally noise regulated area, aircraft noise had more impact in the non-regulated area, due to the larger population. Conclusions: Results suggest associations between community exposure to aircraft noise and the health indicators poor general health status, use of sleep medication, and use of medication for cardiovascular diseases.

Noise Pollution-Sources, Effects and Control

Abstract: The study examines the problem of noise pollution in the wake of its ill effect on the life of the people. A crosssection survey of the population in Delhi State points out that main sources of noise pollution are loudspeakers and automobiles. However, female population is affected by religious noise a little more than male population. Major effects of noise pollution include interference with communication, sleeplessness, and reduced efficiency. The extreme effects e.g. deafness and mental breakdown neither is ruled out. Generally, a request to reduce or stop the noise is made out by the aggrieved party. However, complaints to the administration and police have also been accepted as a way of solving this menace. Public education appears to be the best method as suggested by the respondents. However, government and NGOs can play a significant role in this process.

The role of noise sensitivity in the noise–response relation: A comparison of three international airport studies

Abstract: In order to examine the role of noise sensitivity in response to environmental noise, this paper presents detailed comparisons of socio-acoustic studies conducted around international airports in Amsterdam, Sydney, and London. Earlier findings that noise sensitivity moderates the effect of noise on annoyance were examined to see if they could be replicated in each of the datasets, independent of the technique of measuring noise sensitivity. The relation between exposure to aircraft noise and noise annoyance was studied separately for groups of individuals with low, medium, and high noise sensitivity, with statistical adjustment for relevant confounders. Results support the previous findings that noise sensitivity is an independent predictor of annoyance and adds to the prediction of noise annoyance afforded by noise exposure level by up to 26% of explained variance. There is no evidence of a moderating effect, whereby the covariation between noise exposure level and annoyance is weak for people who score at the extreme high or low end of the sensitivity scale, and strong for people who score in the middle of the sensitivity scale. Generally, noise sensitivity appears to increase annoyance independently of the level of noise exposure after adjustment for relevant confounders. These findings were consistent across the three datasets.

An approach to the acoustic design of outdoor space

Abstract: This paper focuses on soundscape planning, or acoustic design, in the planning and management of open space in both urban and non‐urban areas. It is based on notions, promoted over several decades, that the acoustic aspects of open space can, and should be, subject to design in the same way as are the visual dimensions. The current paradigm for the management of the outdoor acoustic environment is noise control and soundscape planning needs to adopt quite different practices from noise control with respect to acoustic criteria and measurement. The paper explores the specification of acoustic objectives for outdoor soundscapes and the translation of these objectives into acoustic criteria that are amenable to measurement and prediction as part of the design process. Such objectives, termed Proposed Acoustic Environments, focus on the information content in sounds in a particular space and, only indirectly, on characteristics such as level or loudness. Outdoor acoustic design is mostly concerned with avoidi...

Longitudinal surveys on effects of changes in road traffic noise-annoyance, activity disturbances, and psycho-social well-being.

Abstract: The adverse effects of long-term exposure to a high volume of road traffic were studied in socio-acoustic surveys in 1997 and in 1999 after a substantial reduction in road traffic. The results obtained in 1997 showed a similar response pattern as in previously performed studies in the area in 1986 [Ohrstrom, J. Sound Vib. 122, 277–290 (1989)]. In 1999, road traffic had been reduced from 25 000 to 2400 vehicles per day, and this resulted not only in a large decrease in annoyance and activity disturbances, but also in a better general well-being. The results suggest that a reduction in both noise and other pollutants from road traffic contribute to these effects. To be able to use the outdoor environment and to have the possibility to keep windows open is essential for general well-being and daily behavior, which implies that access both to quiet indoor and outdoor sections of the residency is of importance for achievement of a healthy sound environment. More knowledge of long-term health consequences of exposure to noise and simultaneous pollutants from road traffic is needed. Studies should focus more on “softer” health outcomes and well-being than hitherto and preferably be performed in connection with traffic abatement measures.

Relationship between exposure to multiple noise sources and noise annoyance

Abstract: Relationships between exposure to noise [metric: day-night level (DNL) or day-evening-night level (DENL)] from a single source (aircraft, road traffic, or railways) and annoyance based on a large international dataset have been published earlier. Also for stationary sources relationships have been assessed. Here the annoyance equivalents model concerning noise annoyance from combined sources and the underlying assumptions are presented. The model first translates the noise from the individual sources into the equally annoying sound levels of a reference source, road traffic, and then sums these levels giving total level L. The annoyance from the combined sources is found by substituting exposure L in the road traffic exposure-annoyance relationship. The most important assumption, independence of the contributions of the sources, is discussed. It appears that independence will be violated substantially only due to the effect of the presence or absence of a quiet side of a building, which is not incorporated in the model. For use in practice, the application of the model is broken down in five steps. The step by step procedure can be used for the assessment of the total noise level and the associated total annoyance on the basis of the DNL or DENL values of the individual sources.

Children's perceptions of their acoustic environment at school and at home.

Abstract: This paper describes the results of a large-scale questionnaire survey that ascertained children’s perceptions of their noise environment and the relationships of the children’s perceptions to objective measures of noise. Precision, specificity, and consistency of responding was established through the use of convergent measures. Two thousand and thirty-six children completed a questionnaire designed to tap (a) their ability to discriminate different classroom listening conditions; (b) the noise sources heard at home and at school; and (c) their annoyance by these noise sources. Teachers completed a questionnaire about the classroom noise sources. Children were able to discriminate between situations with varying amounts and types of noise. A hierarchy of annoying sound sources for the children was established. External LAmax levels were a significant factor in reported annoyance, whereas external LA90 and LA99 levels were a significant factor in determining whether or not children hear sound sources. Obj...

Noise emission during the first powerboat race in an Alpine lake and potential impact on fish communities

Abstract: In order to assess the effects of high-speed boating on fish communities, noise levels were measured during the first Class 1 powerboat race on the Austrian Lake Traunsee. The noise spectra were compared to natural ambient noise and hearing abilities of four native fish species. Sound pressure levels (SPLs) were significantly elevated during the training heats and the race compared with natural levels, reaching up to 128 dB re 1 μPa (instantaneous SPL) at a distance of 300 m to the powerboats. Continuous equivalent SPLs were significantly lower during training and the pole position race compared to the race itself because fewer boats were simultaneously on the lake. The hearing abilities of the native hearing specialists and generalists were investigated. While carp and roach (two cyprinids) showed enhanced auditory sensitivity typical for hearing specialists, perch and whitefish were much less sensitive to sounds. Comparisons between power boat noise spectra and audiograms showed that the cyprinids can detect the boats up to several hundred meters distance because the main noise energy is well within the most sensitive hearing range. The hearing generalists, however, probably only perceive the first harmonic of the boat noise at close distances.

Exposure to Environmental Urban Noise Pollution in Birmingham, UK

Abstract: This paper examines the extent to which inequalities in noise exposure are present in the city of Birmingham in the English Midlands. Estimates of road and rail noise levels were made using established sound propagation models and were combined with data on noise generated from the city's airport. Demographic details from the 1991 UK Census provided information on population age, ethnic make-up and deprivation. No relationship was established between noise exposure and population age, and there was only rather weak evidence of an association between noise exposure and ethnicity. Similarly weak disparities were observed in estimated noise exposures and levels of socioeconomic deprivation. The implications of these findings with regard to possible efforts to reduce urban noise levels are discussed.

A method to include in lca road traffic noise and its health effects

Abstract: Background, Aims and Scope Transport noise represents an environmental problem that is perceived by humans more directly than the usual chemical emissions or resource uses. In spite of this, traditional LCA applications still exclude noise — probably due to the unavailability of an appropriate assessment method. In order to fill the gap, this article presents a study proposing a new computational procedure for the determination of health impairment resulting from noise emissions of road vehicles.

Environmental rating of vehicles with different alternative fuels and drive trains: a comparison of two approaches

Abstract: Two rating systems assessing the environmental damage caused by vehicles are compared: a Brussels one, ECOSCORE and a European one, CLEANER DRIVE. Both vehicle rating systems were developed for the assessment of vehicles with alternative types of fuels as well as different types of drive train, such as electric, hybrid and fuel cell vehicles. A simplified life cycle assessment following a well-to-wheel approach is used to compare the methodologies. Total emissions involve oil extraction, transport and refinery, fuel distribution and electricity generation and distribution as well as tailpipe emissions from the use phase. Different types of pollution such as acid rain, photochemical air pollution, noise pollution and global warming are examined and their impact on numerous receptors such as ecosystems, buildings and human beings (cancer, respiratory diseases, etc.) are investigated. Examples illustrate both methodologies and sensitivity analysis is used to examine the robustness of the systems.

The marginal values of noise disturbance from air traffic: does the time of the day matter?

Abstract: This paper analyzes the marginal willingness to pay for changes in noise levels related to changes in the volume of flight movements at a city airport in Stockholm, Sweden, by using a choice experiment. When estimating marginal willingness to pay for different times of the day and days of the week, we find that these vary with the temporal dimensions: mornings and evenings have higher marginal values. Interestingly, a substantial proportion of the respondents prefer no changes in the current noise level. The paper concludes with a policy discussion related to incentive-based pricing.

Surveillance of Occupational Noise exposures using OSHA's Integrated Management Information System

Abstract: Background Exposure to noise has long been known to cause hearing loss, and is an ubiquitous problem in workplaces. Occupational noise exposures for industries stored in the Occupational Safety and Health Administration's (OSHA) Integrated Management Information System (IMIS) can be used to identify temporal and industrial trends of noise exposure to anticipate changes in rates of hearing loss. Methods The noise records in OSHA's IMIS database for 1979–1999 were extracted by major industry division and measurement criteria. The noise exposures were summarized by year, industry, and employment size. Results The majority of records are from Manufacturing and Services. Exposures in Manufacturing and Services have decreased during the period, except that PEL exposures measured by federal enforcement increased from 1995 to 1999. Conclusions Noise exposures in manufacturing have been reduced since the late 1970s, except those documented by federal enforcement. Noise exposure data outside manufacturing is not well represented in IMIS. Am. J. Ind. Med. 46:492–504, 2004. Published 2004 Wiley-Liss, Inc.

Surveillance of noise exposure in the Danish workplace: a baseline survey.

Abstract: Aims: To evaluate an epidemiological approach to a national noise hazard surveillance strategy, and report current exposure levels in the Danish workplace. Methods: A study base of 840 companies in 10 selected high risk industries in the largest county in Denmark was identified from a national register. Noise exposure was measured among manual workers recruited from a random sample of workplaces in each industry. For reference, financial companies and a sample of residents were investigated according to the same protocol. The A-weighted equivalent sound level (LAeq) for a full shift was measured by portable dosimeters worn by 830 workers employed at 91 workplaces (67% of 136 eligible companies). Results: The epidemiological design proved feasible and established a baseline for future noise surveillance. Substantial resources were needed to motivate workplaces to enlist and the final participation rate was less than optimal (66.9%). The LAeq (8) values in the selected industries were highly elevated (mean 83.7 dB(A) (95% CI 83.3 to 84.1) in comparison with residents and office workers (mean 69.9 dB(A), 95% CI 68.8 to 71.0). Some 50% of the workers were exposed to more than 85 dB(A) and some 20% to more than 90 dB(A) in several industries. Conclusion: Noise levels in Danish high risk industries remain high. A substantial proportion of workers are exposed to noise levels above the current threshold limit of 85 dB(A). Ongoing surveillance of noise exposure using full shift dosimetry of workers in random samples of workplaces most at risk to high noise levels may help reinforce preventive measures. Such a programme would benefit from compulsory workplace participation.

Noise exposure in orthopaedic practice: potential health risk

Abstract: Noise exposure is one of the major causes of permanent hearing loss in society. Exposure of health service staff to intense levels of noise in the workplace is a potential risk for the development of temporary and permanent hearing loss. In this prospective study, 18 members of the orthopaedic staff underwent hearing assessment by pure tone audiometry and speech discrimination prior to noise exposure at the workplace and immediately following cessation of work. The number of hours of exposure and noise levels in the workplace was also analysed. Only minimal temporary sensorineural threshold shifts were detected post-noise exposure. There was no change in speech discrimination scores and no individuals complained of tinnitus. The number of hours of exposure ranged from 1.5 to 8.5 hours (mean 5.2 hours). Recorded sound levels for instruments ranged from 119.6 dB at source to 73.1 decibels at 3 metres. Although high sound levels are recorded in the orthopaedic operating theatre, the intermittent nature exposure to the intense noise may protect staff against hearing loss, speech discrimination difficulties and tinnitus.

A boundary element approach to acoustic radiation and source indentification

Abstract: Over the past few decades noise pollution has emerged as an important issue in modern society and provides much of the impetus for the development of noise prediction and reduction techniques. The ability to locate different sound radiating sources and to determine their contributions to the overall sound distribution is a first step towards solving the noise problem. This research deals with the development of methods to compute acoustic radiation from a stationary vibrating object and, vice versa, methods to iden- tify the sources of sound on the surface of the object, provided a measurement of the sound field is available.

Noise induced hearing loss among industrial workers in Dar es Salaam.

Abstract: Objectives : To determine whether sound in the study areas was of sufficient intensity to cause hearing loss and if so whether those exposed have been affected and to determine whether workers/employees in the study areas were aware that sound can cause hearing loss and if so whether they knew that this can be prevented by ear protection. Design : Cross-sectional study Setting : Industrial area A and B randomly selected from among industries in Dar es Salaam. Subjects : One hundred and fifty workers from area A and fifty two employees from area B. Method : A questionnaire was filled and had their hearing thresholds measured by a pure tone audiometer machine. Results : In both study areas the noise levels were above the safe limit of 85dB(A). In area A 28 workers and in area B eight employees had noise induced hearing loss. In area A 81.1% of the workers and in area B 85% of the employees knew that noise causes hearing loss. All workers/employees from both study areas knew that noise induced hearing loss could be prevented by some form of ear protection. Conclusion : Workers/Employees exposed to noise above 85dB(A) will eventually develop hearing loss. Workers/employees are aware of this hazard. There is therefore a need to educate those exposed on how best to protect their ears from the hazard and provide them with protective gear. (East African Medical Journal: 2003 80(6): 298-302)

On the influence of core laminations upon power transformer noise

Abstract: Power transformers can be sources of disturbing and annoying acoustic noise. This paper is a first phase report of a wider framework of study that investigates the noise radiation characteristics of air-cooled power transformers. The dynamics of the transformer core structure plays a significant role in the noise generation process. The reported work focuses on the influence of lamination of the core block on its structural dynamic behaviour. The degree of lamination of a core and its boundary conditions have been found to have a strong influence on its resonant behaviour and the need for an accurate modelling of these physical details has been observed through a combined experimental – numerical study. 1. Transformer noise – an annoying disturbance Power transformers are designed for the transmission and distribution of electrical power. Apart from satisfying this functional performance objective, the operation of a transformer happens to induce some annoying acoustic radiation. The requirement for more electrical power associated with the growing density of population, especially in urban areas, has resulted in enhancing the supply capacity of local electrical substations by adding more transformers, or building new substations of high power ratings closer to the neighbourhoods. This may result in the inhabitants in the vicinity being exposed to increased, and often disturbing, noise levels. Transformer acoustic noise is a hum characterised by spectral spikes at harmonics of the fundamental frequency (100 Hz /120 Hz) which is twice the line supply frequency. The transformer’s low frequency tonal noise components are the major source of annoyance and intrusion, invoking noise complaints from the residents, [1, 2]. A growing awareness and concern about public health problems due to noise pollution has brought transformer substations under the purview of tough regulations on excessive noise emission. Therefore, the need for compliance to stricter noise control regulations requires the construction of transformers that are less noise-prone and the design of efficient passive/active control systems for onsite noise control measures. For this purpose, a proper understanding of the noise generation in a transformer and an accurate estimation of its radiation characteristics are necessary.

Workers' perceptions and awareness of noise pollution at construction sites in Kuwait

Abstract: Ample evidence exists that exposure to high noise levels acts as a stressor, which over a long period may result in pathological side-effects. Studies also exist which indicate that the exposure of construction site workers to noise pollution is significantly greater than that of the public at large. Despite the enormous post-invasion growth in the construction of residential projects in the State of Kuwait, no study of construction noise pollution and workers' perceptions and awareness levels of this pervasive urban problem has been performed in Kuwait or in the Middle-East region. This research project has attempted to narrow this information gap. A systematic-randomly selected sample of 26 construction projects were monitored for noise pollution levels. More than 500 workers at the selected sites were also person-surveyed for their perceptions and awareness of construction noise. Although the measured noise levels were frequently and significantly above standard outdoor noise levels (especially the hig...

Levels and Influencing Factors of Noise Pollution from Small-Scale Industries (SSIs) in a Developing Country

Abstract: A study was carried out to determine levels and factors that influence noise pollution from small-scale industries (SSIs) in Dar es Salaam City Tanzania. Two sites for wood- and metalworks industries were investigated. Both sites exhibited equivalent noise levels higher than 90.0 dBA, the permissible exposure level limit for occupational noise. At a woodworks SSI, noise levels were found to correlate well with machine-use age, wood-feed speed, and wood-cut depth. Additionally, noise emanating from both types of SSIs was found to influence the level of environmental noise in the neighborhood of the SSIs. One woodworks SSI was found to have a circle of influence of about 140 m. The study concluded that SSIs present a serious source of environmental noise pollution in their neighborhoods. Noise pollution from SSIs is greatly influenced by the type of SSIs and the activities they carry out, the type and age of machines they use, their location relative to residential areas in their vicinity, and in-house noise control measures.

Environmental Impacts due to Urban Transport

Abstract: Private cars, trucks and buses are the main contributors to air pollution in urban areas. This chapter presents the problems of environmental pollution caused by urban transport, including air and noise pollution in the local environment, together with global warming.

Fourier based high-resolution near-field sound imaging

Abstract: Noise pollution is a generally acknowledged problem in modern day society. The current tendencies towards lightweight and cheaper product design are primarily responsible for increasing nuisance, annoyance and environmental problems caused by acoustic noise. There are several reasons for research towards technologies that facilitate acoustic noise reduction. Nowadays, low noise design of consumer electronics, high-tech systems and automotive are restricted to increasingly stringent regulations and quality aspects. Effective countermeasures in order to reduce sound radiation are only taken when the source of sound is known. "Inverse Acoustics" is a very effective method to visualize and quantize the sound sources, which reconstructs source information based on measurements away from the source, yet in the near-field. In fact, the system is able to reconstruct the entire acoustic message that a source radiates in the direction of interest. The current methods for source reconstruction produce sound images with very little detail, they often require cumbersome numerical calculations and models, and they are often highly impractical for industrial applications. This research focuses on fast and accurate measurement and signal processing methods for inverse acoustics that are applicable in practical situations which require high resolutions under hazardous acoustic conditions. The inverse process is based upon spatial and wavenumber domain Fourier techniques, also referred to as Near-field Acoustic Holography. More in detail, spatial properties with respect to aliasing, leakage, signal-to-noise ratio and sensor set-ups are investigated and explicit methods and rules are developed to assist in proper determination of the acoustic holograms. In order to correctly transform the spatial hologram data into the wavenumber domain or k-space, a method called border-padding is developed. This method, which is an alternative to spatial windowing, is highly accurate without slowing down the processing time considerably. Another important factor is regularization, which is required since the inverse process is highly ill-posed. Without proper filtering action taken, noise blows up as the hologram-source distance or the wavenumber grows. In this research project a method is developed to automatically determine the proper filter function and filter parameters, which is a near-optimal trade-off between noise blow-up and deterioration of useful source information. These important properties are combined in a fully automated near-field sound imaging system design. At the Technical University of Eindhoven two versions of this system were developed and built; a large version that is based in the semi-anechoic room of the laboratory and a portable system that is suitable for small electronic devices and high-tech systems. A number of practical cases are used to qualitatively as well as quantitatively validate the improvements with respect to existing methods and illustrate the possibilities for industrial application.

Annoyance with aircraft noise in local recreational areas, contingent on changes in exposure and other context variables.

Abstract: Few socioacoustic studies have examined the effect of noise on outdoor recreationists. The areas studied have been mountain and wilderness areas that people typically travel for a distance to visit. In this article we examine the reactions to aircraft noise in local recreational areas experiencing either decreased (1930 survey respondents), or increased noise exposure (1001 survey respondents). Field studies were conducted before and after the relocation the main airport of Norway in 1998 in one area near each airport. The relationship between individual noise exposure (LAeq for the aircraft events, percentage of time aircraft were audible, and LAsel) for the aircraft events. The analyses included the “situation” in which data were collected (before or after the relocation), and variables describing the recreational context. A strong effect of the “situation” was found in both cases, but the size of the effect was influenced by the choice of exposure variable in one of the study areas. Other context varia...

Airport noise and residential housing valuation in southern California: A hedonic pricing approach

Abstract: A large and detailed data set is used to examine the influence of airports and airport light paths on housing prices. The results indicate that individuals consider airport proximity and airport flight patterns in their housing purchases. This shows that there exist two distinct measurable price gradients that distinguish large airports from small airports. In addition, homes located under the flight path of a large airport have a price gradient that is significantly larger than homes located under the flight path of a small airport.

A Quest for Quiet Commercial Passenger Transport Aircraft for Take-off and Landing

Abstract: Noise pollution in communities living close to airports world-wide could have been avoided if, following the Second World War, Governments and Local Planners had built the very large commercial airports according to strong directives and regulations preventing the building of houses in zones closer than 2 − 3km from the airport boundary fence. Today the problem of noise nuisance in communities living close to airports is world-wide. The noise nuisance during the approach to landing is set by CTOL aircraft following the 3deg. ILS glide slope. All commercial aircraft thus fly at high lift, referred to as the ‘dirty configuration’, from a height of about 300m. altitude to touchdown, a distance of about 6km., including the dropping of the undercarriage while the aircraft is flying low over residential areas. The noise on the ground far exceeds the noise of a ‘clean aircraft’ if such an aircraft could fly at the same approach speeds. This paper reviews possible future aircraft technology that could avoid aircraft flying low over residential areas and so permit the introduction of a mandatory height exclusion zone of at least 1000m. above all residential areas. It is found that the use of STOL aircraft incorporating circulation control, and preferably integrated lift and propulsion systems could be designed to meet this objective and would allow the undercarriage to be lowered during a continuous descent much closer to the airport boundary fence. Further research is required to ensure such aircraft make no increase in noise over current CTOL aircraft operating at the same distance. Since the STOL aircraft will be flying higher and slower, and its take-off and landing distance will be shorter, the noise reduction from this greater separation in distance from residential ares would result in noise reductions in these communities of at least 20dB, a target which has become the International goal for aircraft noise reduction in current research programs.