Change of acoustic characteristics caused by platform screen doors in train stations

Railway companies are encouraged to install platform screen doors (PSDs) for safety reason in Japan. The PSDs might affect train noises in stations, but the effects are not well understood. The aim of the present study is to clarify the effects of PSDs on acoustic characteristics. PSDs can be principally classified by two types, i.e., mobile full-height (MFH) and mobile half-height (MHH). Train noises were recorded in ground and underground train stations with MFH, MHH and without PSDs. The noises were evaluated by noise level, the maximum peak of the interaural cross-correlation function (IACC), and the width of the first decay (W_Φ(0)) of the autocorrelation function. Noise level emitted by trains was reduced by PSDs in both aboveground and underground stations. IACC was decreased by PSDs in both ground and underground stations, suggesting that PSDs made train noises more diffused. W_Φ(0) was decreased by PSDs in both ground and underground stations, which means that the train noises in station with PSDs have higher spectral centroid, suggesting that the PSDs blocked the lower frequency components of train noises.     

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.     

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.     

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.     

Influence of turbulence on train noise

The subject of this paper is the long distance propagation of train noise. The sound exposure level of train noise L_AE was measured. To describe the results of measurements, a semi-analytical model was used. It takes into account the wave-front divergence, air absorption, ground effect, and the turbulence destroying the coherent nature of the ground effect. The model contains three adjustable parameters that must be estimated at the site. To verify the model, we performed measurements of L_AE at the distance D = 450 m from the train track center. The difference between the calculated and measured mean values of L_AE equals 1.3 dB.     

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.     

典型城市地铁站台噪声满意度*

地铁是城市轨道交通重要组成部分,地铁站台噪声对乘客身心健康有重要影响。以合肥轨道交通一号线为例,具体选择地下侧式、地下双岛式和地下岛式3个典型空间类型的地铁站台为研究对象,通过噪声测量和问卷调查相结合的方法,针对地铁在不同运营时段的乘客站台噪声满意度与噪声声元素舒适度进行评价,探讨性别、声元素舒适度以及站台噪声对乘客噪声满意度的影响。结果表明：对地铁站台噪声满意度评价,乘客性别差异不显著;在乘车高峰期时段,地铁站台广播提示声、地铁工作人员吹哨声、列车进站声和列车出站声是影响乘客站台噪声满意度主观评价的主要噪声声元素;乘客噪声满意度主观评价与站台噪声值呈强负相关,噪声值越高,满意度越低;乘客噪声满意度为可接受时的地铁站台噪声阈值,在乘车高峰期时段为74 dB(A),非高峰期时段为67 dB(A)。该文工作可为城市地铁站台噪声满意度评价及其空间结构设计提供科学参考。     

Assessment criterion for indoor noise disturbance in the presence of low frequency sources

Several studies have presented the effects of environmental noise in and around buildings and communities in which people live and work. In particular, the noise introduced into a building is mostly evaluated using the A weighted sound pressure level (L_Aeq) as the only parameter to determine the perceived disturbance. Nevertheless, if noise is produced by activities or sources characterised by a low frequency contribution, the measurement of L_Aeq underestimates the real disturbance, in particular during sleeping time.     

Annoyance of noise stimuli in relation to the spatial factors extracted from the interaural cross-correlation function

While considering auditory-brain model for subjective responses, effects of spatial factors extracted from the interaural cross-correlation function (IACF) on annoyance of noise stimuli are examined. The previously developed indices to measure sound pressure levels (SPL) and frequency characteristics cannot fully explain the psychological effects of noise. In the first experiment, subjects judged their annoyance by changing fluctuations in the magnitude of interaural cross-correlation function (IACC) and the SPL. In the second, they judged their annoyance by changing fluctuations in the interaural time delay (τ_IACC) and the SPL. Results show that: (1) annoyance increased by increasing the fluctuations of IACC as well as the SPL, (2) annoyance increased by increasing the fluctuations of τ_IACC as well as the SPL.     

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.     

Comparison between old and new noise standards in Nagoya City

The Japanese Environmental Agency (now the Ministry of the Environment) updated the environmental quality standards for noise in April 1999. The new standards replaced the median value of percentile level L₅₀ for noise evaluation with the equivalent sound pressure level L_Aeq. The standards renewed the classification of areas and time sections. The most significant change was the introduction of category of artery-road-adjacent area.This report sets the range of the artery-road-adjacent area to 20 m or less from the applicable road to compare the new standards with the old, based on data collected in Nagoya City. The achieved rates for the new standards seem to be on the whole the same as those for the old standards. However, a detailed analysis reveals some differences, such as higher achieved rates in the artery-road-adjacent areas and lower achieved rates in the general areas for the new standards than for the old.     

The Okinawa study: an estimation of noise-induced hearing loss on the basis of the records of aircraft noise exposure around Kadena Air Base

Aircraft noise measurements were recorded at the residential areas in the vicinity of Kadena Air Base, Okinawa in 1968 and 1972 at the time of the Vietnam war. The estimated equivalent continuous A-weighted sound pressure level L_Aeq for 24 h was 85 dB.The time history of sound level during 24 h was estimated from the measurement conducted in 1968, and the sound level was converted into the spectrum level at the centre frequency of the critical band of temporary threshold shift (TTS) using the results of spectrum analysis of aircraft noise operated at the airfield. With the information of spectrum level and its time history, TTS was calculated as a function of time and level change. The permanent threshold shift was also calculated by means of Robinson's method and ISO's method. The results indicate the noise exposure around Kadena Air Base was hazardous to hearing and is likely to have caused hearing loss to people living in its vicinity.     

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.     

Annoyance and self-reported sleep disturbances due to structurally radiated noise from railway tunnels

In Norway, the requirement for structure borne noise from tunnels is L_pAFmax = 32 dB inside dwellings. According to the Norwegian Standard 8175 it is expected that up to 20% of the exposed population are disturbed by the noise at this level. However, the scientific basis for this noise limit is poor. The aim of this study was to determine the degree of annoyance and self-reported sleep disturbances as a function of L_pAFmax. In the present study, 521 dwellings exposed to structural sound from railway rock-tunnels were identified. A questionnaire was sent to one randomly selected person above 18 years of age from each dwelling. The results showed that both noise induced annoyance and reported sleep disturbances were significantly related to L_pAFmax. Other factors that increased the annoyance were high pass-by frequency of freight trains per day, and degree of sound insulation of the windows. At L_pAFmax = 32 dB, 20% were slightly or more than slightly annoyed, and 4% were moderately or more than moderately annoyed. According to the pre-existing assumption that up to 20% of the exposed population are disturbed by the noise at this level, the present results give support to the Norwegian noise limit L_pAFmax = 32 dB inside dwellings of structure borne noise from railway tunnels.     

The impact of urban noise on primary schools. Perceptive evaluation and objective assessment

This paper aims to assess the impact of environmental noise in the vicinity of primary schools and to analyze its influence in the workplace and in student performance through perceptions and objective evaluation. The subjective evaluation consisted of the application of questionnaires to students and teachers, and the objective assessment consisted of measuring in situ noise levels. The survey covered nine classes located in three primary schools. Statistical Package for Social Sciences was used for data processing and to draw conclusions. Additionally, the relationship of the difference between environmental and background noise levels of each classroom and students with difficulties in hearing the teacher’s voice was examined. Noise levels in front of the school, the schoolyard, and the most noise-exposed classrooms (occupied and unoccupied) were measured. Indoor noise levels were much higher than World Health Organization (WHO) recommended values: L_Aeq,30min averaged 70.5 dB(A) in occupied classrooms, and 38.6 dB(A) in unoccupied ones. Measurements of indoor and outdoor noise suggest that noise from the outside (road, schoolyard) affects the background noise level in classrooms but in varying degrees. It was concluded that the façades most exposed to road traffic noise are subjected to values higher than 55.0 dB(A), and noise levels inside the classrooms are mainly due to the schoolyard, students, and the road traffic. The difference between background (L_A95,30min) and the equivalent noise levels (L_Aeq,30min) in occupied classrooms was 19.2 dB(A), which shows that students’ activities are a significant source of classroom noise.     

Road traffic noise mitigation strategies in Greater Cairo, Egypt

This study concerns road traffic noise in Greater Cairo, Egypt. Road traffic is the most significant sources of noise in the city. Measurements of road traffic noise levels in Greater Cairo in September and October 2001, indicated that noise levels in city were higher than those set by the Egyptian noise standards and policy to protect public health and welfare in residential areas (L_Aeq=80 dB and higher were recorded). A social survey carried out simultaneously indicated that 73.8% of respondent residents were highly or moderately irritated by road traffic noise. In our paper we present (1) The results of road traffic noise measurements. (2) Egyptian noise standards and policy. (3) Results of the social survey. (4) Traffic congestion and traffic noise characteristics of Greater Cairo. (5) Thirty years of countermeasures taken. (6) Future mitigation strategies aiming for a quiet city.     

Noise characteristics of tractors and health effect on farmers

An investigation was conducted to determine the noise propagation (under stationary condition) and noise at operator’s ear level of popular 18.7 and 26.1 kW tractors and 4.6 and 6.7 kW hand tractors during field operations with various implements. It was observed that both tractors produced the noise of 92 dB(A) L_eq in the working zone of operator. The sound pressure level (SPL) of the hand tractor was about 2 dB(A) L_eq higher than that of the tractor. The SPL during field operations at operator’s ear level increased with increase in engine speed and forward speed. Furthermore, the SPL was higher for field operations corresponding to the implement requiring higher draft. It was observed that the SPLs of the tractors and hand tractors were more than the exposure limit of noise for 8-h workday recommended by ISO and OSHA. This may cause health problems to the farmers in the long run.     

DIAGNOSTIC SYSTEM BASED ON THE HUMAN AUDITORY-BRAIN MODEL FOR MEASURING ENVIRONMENTAL NOISE—AN APPLICATION TO RAILWAY NOISE

Measurements of railway noise were conducted by use of a diagnostic system of regional environmental noise. The system is based on the model of the human auditory-brain system. The model consists of the interplay of autocorrelators and an interaural crosscorrelator acting on the pressure signals arriving at the ear entrances, and takes into account the specialization of left and right human cerebral hemispheres. Different kinds of railway noise were measured through binaural microphones of a dummy head. To characterize the railway noise, physical factors, extracted from the autocorrelation functions (ACF) and interaural crosscorrelation function (IACF) of binaural signals, were used. The factors extracted from ACF were (1) energy represented at the origin of the delay, Φ (0), (2) effective duration of the envelope of the normalized ACF, τe, (3) the delay time of the first peak, τ₁, and (4) its amplitude,ø₁ . The factors extracted from IACF were (5) IACC, (6) interaural delay time at which the IACC is defined, τ_IACC, and (7) width of the IACF at the τ_IACC,W_IACC . The factor Φ (0) can be represented as a geometrical mean of energies at both ears as listening level, LL.     

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.     

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.