Sleep disturbance caused by meaningful sounds and the effect of background noise

To study noise-induced sleep disturbance, a new procedure called “noise interrupted method”has been developed. The experiment is conducted in the bedroom of the house of each subject. The sounds are reproduced with a mini-disk player which has an automatic reverse function. If the sound is disturbing and subjects cannot sleep, they are allowed to switch off the sound 1 h after they start to try to sleep. This switch off (noise interrupted behavior) is an important index of sleep disturbance. Next morning they fill in a questionnaire in which quality of sleep, disturbance of sounds, the time when they switched off the sound, etc. are asked. The results showed a good relationship between L_Aeq and the percentages of the subjects who could not sleep in an hour and between L_Aeq and the disturbance reported in the questionnaire. This suggests that this method is a useful tool to measure the sleep disturbance caused by noise under well-controlled conditions.     

Estimating the model-specific uncertainty of aircraft noise calculations

Aircraft noise contours are estimated with model calculations. Due to their impact, e.g., on land use planning, calculations need to be highly accurate, but their uncertainty usually remains unaccounted for. The objective of this study was therefore to quantify the uncertainty of calculated average equivalent continuous sound levels (L_Aeq) of complex scenarios such as yearly air operations, and to establish uncertainty maps. The methodology was developed for the simulation program FLULA2. In a first step, the partial uncertainties of modelling the aircraft as a sound source and of modelling sound propagation were quantified as a function of aircraft type and distance between aircraft and receiver. Then, these uncertainties were combined for individual flights to obtain the uncertainty of the single event level (L_AE) at a specified receiver grid. The average L_Aeq of a scenario results from the combination of the L_AE of many single flights, each of which has its individual uncertainties. In a last step, the uncertainties of all L_AE were therefore combined to the uncertainty of the L_Aeq, accounting also for uncertainties of the number of movements and of prognoses. Uncertainty estimations of FLULA2 calculations for Zurich and Geneva airports revealed that the standard uncertainty of the L_Aeq ranges from 0.5 dB (day) to 1.0 dB (night) for past-time scenarios when using radar data as input, and from 1.0 dB (day) to 1.3 dB (night) for future scenarios, in areas where L_Aeq ⩾ 53 dB (day) and L_Aeq ⩾ 43 dB (night), respectively. Different uncertainty values may result for other models and/or airports, depending on the model sophistication, traffic input data, available sound source data, and airport peculiarities such as the specific aircraft fleet or prevailing departure and arrival procedures. The methodology, while established for FLULA2 on Zurich and Geneva airports, may be applied to other models and/or airports, but the partial uncertainties have to be specifically re-established to account for individual models and underlying sound source data.     

Nocturnal road traffic noise assessment and sleep research: The usefulness of different timeframes and in- and outdoor noise measurements

In this paper, we investigated the procedure of noise assessment in the study of nocturnal noise exposure during sleep in the home situation. The use of two different timeframes (fixed from 11 PM to 07 AM versus personal “Time in Bed” period) was explored as well as the relation between indoor and outdoor noise levels and between the actual and estimated noise levels. Noise recordings were performed inside and outside the bedroom of 24 subjects living in high density road traffic noise areas in the Brussels’ Capital Region during seven consecutive days. Indoor and outdoor noise indicators L_Aeq, L_Amax and individual noise events were analysed. Subjects completed a daily sleep log in which the Time in Bed period was assessed. The results indicate that, for outdoor noise assessment, the use of an average L_Aeq might not be sufficient to reflect well the noise levels during the sleep period. For indoor measurements, significant differences were found in the comparison between both timeframes (L_Aeq: T = 16; p < .001). Considering the relation between indoor and outdoor measurements, low correlations (r = .49; p < .001) were found even when the location of the bedroom as a mediating factor was accounted for (street side; r = .52; p < .001). Therefore, from our study, caution is needed when relying on outdoor noise measurements for the evaluation of sleep disturbances. Furthermore, one needs to be aware of the weak correspondence between indoor and outdoor noise levels in the discussion of what a harmonized noise indicator for the evaluation of noise exposure and sleep disturbances should consist of.     

Urban ambient outdoor and indoor noise exposure at home: A population-based study on schoolchildren

To investigate residential exposure to environmental noise among children in an urban area, a noise measurement campaign was performed at the residences of 44 schoolchildren. Outdoor and indoor noise levels were simultaneously recorded during one week inside and outside each child’s bedroom and in the other room where each child spent most of his or her time, called “the main room”. Associations between equivalent noise levels and familial or environmental characteristics were explored.The recorded equivalent continuous sound levels (L_Aeq) were prone to large variability between dwellings regardless of the measurement location and time of day. Factors linked to outdoor noise level differed from those associated with indoor noise level. Indoor noise levels were associated with the number of children present and noise sources present in the dwelling, whereas outdoor L_Aeq depended significantly on the socio-economic status (SES) of the household. An association was found between the type of view from the window and outdoor L_Aeq, but no significant association was observed between view from the window and indoor L_Aeq. These results support a complex link between noise exposure and the characteristics of the dwelling and of the family, and highlight the contribution of the indoor noise sources to the ambient noise level.Considering the observed acoustic levels and their variability, the sensitivity of children to noise, and the length of time they spend at home, research efforts are needed to better quantify noise exposure at home if the actual burden of noise on child health is to be identified.     

Reactions to railway noise in Denmark

People's reactions to railway noise were studied along seven Danish railway lines with traffic intensities from 30 to about 300 trains per 24 hours. The calculated sound levels varied between 43 and 71 dB(A) for L_Aeq,24h and between 78 and 102 sB(A) for L_Amax. 615 persons were interviewed. One third of these felt strongly or somewhat annoyed by the railway noise. The relations between the noise level and the extent of annoyance or various kinds of behaviour (telephone conversation, TV-listening, opening of windows, sleep, etc.) were found. The relations were found for both L_Aeq,24h and L_Amax, but the correlation for L_Amax is generally bad. Noise in the evenings was found to be more annoying than noise in other daytime periods. More than half of the interviewees answered that goods trains especially were a problem. People exposed to noise at their place of work seem to feel more annoyed by railway noise than other people.     

Characteristics of train noise in above-ground and underground stations with side and island platforms

Railway stations can be principally classified by their locations, i.e., above-ground or underground stations, and by their platform styles, i.e., side or island platforms. However, the effect of the architectural elements on the train noise in stations is not well understood. The aim of the present study is to determine the different acoustical characteristics of the train noise for each station style. The train noise was evaluated by (1) the A-weighted equivalent continuous sound pressure level (L_Aeq), (2) the amplitude of the maximum peak of the interaural cross-correlation function (IACC), (3) the delay time (τ₁) and amplitude (?₁) of the first maximum peak of the autocorrelation function. The IACC, τ₁ and ?₁ are related to the subjective diffuseness, pitch and pitch strength, respectively. Regarding the locations, the L_Aeq in the underground stations was 6.4 dB higher than that in the above-ground stations, and the pitch in the underground stations was higher and stronger. Regarding the platform styles, the L_Aeq on the side platforms was 3.3 dB higher than on the island platforms of the above-ground stations. For the underground stations, the L_Aeq on the island platforms was 3.3 dB higher than that on the side platforms when a train entered the station. The IACC on the island platforms of the above-ground stations was higher than that in the other stations.     

Estimation of the long term average sound level from hourly average sound levels

It is shown how to estimate the long-term average sound level, L_AeqLT (for free flowing road traffic) from measurements of the hourly A-weighted equivalent sound level, L_Aeq1h. To estimate the parameters of the model which describe noise emission and attenuation, concurrent measurements of L_Aeq1h at two distances from the considered road are needed. A semi-empirical formula is derived for L_AeqLT approximation. Also the uncertainty of this approximation is given as a function the distance from the road and receiver height.     

Estimating traffic noise for inclined roads with freely flowing traffic

Traffic noise measurements on the kerbs of 19 independent inclined trunk roads with freely flowing traffic within the residential areas of Hong Kong are carried out in the present investigation. The performance of the existing noise prediction models in predicting traffic noise from inclined roads is evaluated. By regression analysis and simple physical consideration of the traffic noise production mechanisms, formulae for the prediction of the L_A10, L_A50, L_A90 and L_Aeq are developed or re-calibrated. Results suggest tyre noise has the major contribution to the overall noise environment when the source is an inclined trunk road. Also, the road gradient is found to have a higher contribution to the traffic noise than assumed in the existing models, but becomes unimportant when the background noise level L_A90 is concerned.     

Road traffic noise attenuation by belts of trees

Measurements were made at a number of sites of road traffic noise propagating through belts of trees and bushes and above grass-covered ground, respectively. The belt widths were between 3 and 25 m. The distance from the road to the front of the belts also varied from site to site. The microphones were placed 1·5 m above the ground. A comparison between attenuations obtained, expressed as differences in equivalent constant A-weighted sound pressure levels, L_Aeq, showed no significantly higher attenuation values for propagation through belts of trees than for propagation above grass-covered ground. Only in the frequency range above 2 kHz were attenuations significantly higher through the belts of trees and bushes. The belts of trees selected consisted mainly of deciduous trees and bushes between 5 and 10 years of age. Such types and widths are representative of what could often be used in normal urban situations in an attempt to provide practical noise reduction. According to the results of this investigation, however, these do not significantly reduce L_Aeq 1·5 m above the ground. Planting of belts of trees and bushes between roads and dwellings might influence the environmental quality of residential areas due to nonacoustic factors or reduce nuisance due to spectral changes not affecting L_Aeq. This has not been investigated.     

Noise mapping at different stages of a freeway redevelopment project – A case study in Brazil

In economically developing countries such as Brazil, India and China, rising levels of noise pollution are associated with the accelerated growth of cities and the increasing circulation of automotive vehicles. This paper presents the results of an acoustic evaluation conducted in areas adjacent to federal highway BR-116, part of which lies within the urban limits of the city of Curitiba in southern Brazil. In situ measurements were taken of the noise levels, from which noise maps were drawn in different stages of the implementation of the road restructuring project called the Green Line. After calibration, a computational model was used to evaluate an operational scenario of the highway in the future. The results of the mappings were compared with reference noise emission values established by municipal legislation. The maps revealed the existence of noise pollution in the urban stretch of the federal highway in all the scenarios [L_Aeq > 65 dB(A)]. Efforts to control environmental noise in cities are aided by computational models for urban planning. These models are extremely helpful for environmental management and decision-making by public authorities for solutions to potential environmental risks, as is the case of urban noise.     

The effect of the number of aircraft noise events on sleep quality

BackgroundBoth the WHO and the EC recommend the use of L_night as the primary indicator for sleep disturbance. Still, a key question for noise policy is whether the prediction of sleep quality could be improved by taking the number of events into account in addition to L_night.ObjectivesThe current paper investigates the association between sleep quality and the number of aircraft noise events. The first aim of this study was to investigate whether, for the purpose of predicting sleep quality measured by motility, the nummer of events is adequately represented in L_night for the purpose of predicting sleep quality measured by motility. The second aim was to investigate whether the number of events at a given L_night has an additional predictive value. In addition, it was explored whether the total number of events should be taken into account for the production of sleep quality, or only the number of events exceeding a certain sound pressure level.MethodsThis study is based on data of a field study among 418 people living within a range of 20 km from Amsterdam Airport Schiphol. The data from this study are well suited for this purpose, since for every subject both the number and the exposure level of events are available. Sleep quality was measured by motility, derived from actimeters worn on the wrist, and by self-reported sleep quality scored on a 11-point scale. Mixed linear regression models were built in a stepwise manner to predict sleep quality during a sleep period time.ResultsThe results show that, given a certain equivalent noise level, additional information on the overall number of events does not improve the prediction of sleep quality. However, the number of events above L_Amax of 60 dB was related to an increase in mean motility, indicating lower sleep quality. No effect of number of events was found on self-reported sleep quality.ConclusionsThis study suggests that the number of events is more or less adequately represented in L_night and only the number of high noise level events may have additional effects on sleep quality as measured by motility. This may be viewed as an indication that, in addition to L_night, the number of events with a relatively high L_Amax could be used as a basis for protection against noise-induced sleep disturbance.     

DIFFERENT EFFECTS OF ROAD TRAFFIC NOISE AND FROGS' CROAKING ON NIGHT SLEEP

This study was designed to assess the effects of road traffic noise and frogs' croaking on the objective and subjective quality of sleep in a laboratory. The subjects were seven male students aged 19-21 years. They were exposed to recorded road traffic noise and frogs' croaking, with 49·6 and 49·5 dB(A)L_Aeq , and 71·2 and 56·1 dB(A) L_Amax, respectively. The background noise in the experimental room was 31·0 dB(A) L_Aeq. The sleep EEG was recorded according to standard methods. The sleep polygraphic parameters examined were the percentage of sleep stage relative to the total sleep time (%S1, %S2, %S(3+4), %SREM, %MT), total sleep time, sleep onset latency, and awakening during sleep in minutes and sleep efficiency. A structured sleep rating questionnaire (OSA), was administered to the subjects after they awakened. The %S2 increased and the %SREM decreased during exposure to road traffic noise. However, no significant effect of exposure to frogs' croaking was observed on any of the polygraphic sleep parameters. The subjective quality of sleep was degraded more by exposure to road traffic noise than that to frogs' croaking.     

A study of noise in CNG driven modes of transport in Delhi

Measurements of noise and its spectral characteristics were made inside various types of transport running on Compressed Natural Gas (CNG) fuel in Delhi. Noise indices L₁₀, L₅₀, L₉₀ and L_eq were estimated from the measured noise levels for vehicles in neutral gear, slow speed (speed ?20 km/h) and under free flow (speed ?30 km/h) conditions. It is found that background levels, when averaged over all speeds, are maximum in Rural Transport Vehicles (RTV) followed by Buses, Auto-rickshaws and Taxis. With increase in the speed, noise levels are appreciably enhanced except in the case of auto-rickshaws where the increase is moderate. The spectral distributions of noise inside vehicles obtained at 1-octave band frequencies, show a rather similar nature. The study reveals significantly lower noise levels inside CNG driven public modes of transport compared to those found in an earlier survey inside diesel and petrol driven vehicles.     

Psychological evaluation of sound environment in a compartment of a high-speed train

Sound environment in a compartment of high-speed trains (Shinkansen) was examined in relation to speech communication and annoyance. Three experiments were conducted. In Experiment 1, the annoyance caused by the compartment noise was judged. In Experiment 2, both the compartment noise and the conversation were presented together and the annoyance of the combined sounds was judged. In Experiment 3, both sounds were presented and only the disturbance of conversation was judged. The results showed that: The annoyance of compartment noise showed good correlation with L_Aeq. The annoyance of the combination of the compartment noise (N) and the conversation (C) increased as C/N decreased. There was, however, a tendency that annoyance increased as C/N increased in some conditions. This suggests that there exists an optimum level of compartment noise at 50-60 dBA taking the level of conversation into consideration. The disturbance of the conversation increased as C/N increased. However, when the level of conversation became high, it was judged as being disturbing regardless of the level of compartment noise.     

Long term sleep disturbance due to traffic noise

This contribution to the evaluation of the effects of traffic noise on sleep disturbance is focused on the responses of people living near a main road. Experiments were carried out in the homes of subjects who had habitually been exposed to noise for periods of more than four years. The chronic changes in overall sleep patterns and the temporary sleep responses to particular noise events caused by traffic are demonstrated. Young people show mainly stage 3 and 4 deficits whilst older people show REM sleep deficits. The cardiac response to noise during sleep was also examined. These results highlight that both long term average and peak levels are important in assessing sleep disturbance. The threshold levels, measured inside the bedroom and above which sleep quality starts to become impaired, are 37 L_eq(A) and 45 dB (A)L_{p max}, respectively. For the type of traffic studied these two levels are coherent and it is therefore possible that a single noise index, L_eq(A), is sufficient to scale sleep disturbance.     

THE EFFECT OF DIFFERENT KINDS OF NOISE ON THE QUALITY OF SLEEP UNDER THE CONTROLLED CONDITIONS

Many laboratory and field studies of the effect of noise on sleep have been performed where subjects sleep whole nights. It was suggested from our former studies that the most serious effect of noise on sleep is disturbance in falling asleep and that people have to make efforts to try to sleep in noisy situations. In this study, the effort to fall asleep was used as an index of sleep and the effect of various physical properties of sounds was examined. Subjects were asked to try to sleep listening to sounds presented with a mini-disk and they were allowed to switch off the sound after 1 h if they could not sleep. The results suggest that (1) whether subjects can sleep within 1 h after they start to try to sleep is a good index of the effect of noise on sleep and that L_Aeqis a good index of the effect of noise on sleep except for the sounds which have meanings such as songs and people's talk.     

Evaluation and analysis of the environmental noise of Messina, Italy

In this paper, the results of a study on the environmental noise pollution of the city of Messina (Italy) are presented. The investigation has included a preliminary classification of the territory in six acoustically homogeneous areas according to Italian noise regulations. On the basis of the resultant acoustic zoning 35 sites were selected for an experimental survey. This last has been carried out by extensive measurements of the main indexes for noise pollution (L_eq, L₁, L₁₀, L₅₀, L₉₀, L₉₉) and of the traffic flow and composition. Results indicate that: (a) main roads of Messina are overloaded by traffic flow during day-time period and that in all the examined sites daily average sound levels due to road traffic exceed environmental standards by about 10 dBA; (b) environmental noise exhibits a certain degree of spatial variance resulting primarily from the peculiar geo-morphological structure of the town and from the transport infrastructure and (c) more than 25% of residents should be highly disturbed by road traffic noise.     

Noise map validation by continuous noise monitoring

This paper presents a comparison of two noise assessments in the Gdansk agglomeration in Poland. One is based on the noise map produced by computational method for the city in 2007, the second one is based on real data from continuous measurements acquired by a noise monitoring network operating in the city since 2008. Differences are shown and analyzed. Additionally, seasonal and weekday influence on noise indicators (L_DEN, L_D, L_E and L_N) is analyzed and discussed in this paper.