Noise dosimeter for monitoring exposure to impulse noise

Commercially available noise dosimeters do not perform properly in impulsive noise environments because they suffer from instrumentation limitations and lack metrics that characterize impulse noise. In this paper, a design concept is proposed for an impulse noise monitoring dosimeter that addresses the current dosimeter’s limited capabilities and describes the various parameters that can appropriately be used to measure and evaluate exposure to impulse noise. The design concept is based on the accurate acquisition and storage of the original impulse waveform. For data analysis (using MATLAB) and calculation of “impulse noise metrics,” National Institute for Occupational Safety and Health (NIOSH) used a prototype impulse noise dosimeter system that consisted of a Bruel&Kjaer 4136 microphone and a Panasonic Digital Audio Tape Recorder. The proposed instrument would enable collection of data for validation of presently defined and yet to be defined metrics quantifying noise-induced permanent threshold shifts (NIPTS) resulting from impulse/impact exposures. It will also enable occupational safety and health professionals to make accurate measurements of ultimately approved metrics.     

Noise mitigation action plan of Pisa civil and military airport and its effects on people exposure

The “Galileo Galilei” airport is a civil and military airport quite close to central Pisa. Although the airport brings benefits in terms of tourism and different types of income, the air traffic growth exacerbates the exposition to aircraft noise. This could significantly affect public health. To this day, a small number of studies takes into account the standard indicators of Europe by considering noise emission data for military aircrafts. We estimated the noise impact produced by the airport and we evaluated the related exposed population by using the Integrated Noise Model (INM). The noise power levels of both commercial and military flights have been considered as an input to the model. Predicted levels were validated by means of a noise-monitoring network. A new tracking system (AirNav Radar) that captures Automatic Identification System (AIS) signals emitted by each aircraft has been used to emulate takeoff and landing procedures. This improves the accuracy of the input to the model. We simulated noise maps for present and future scenarios, including those following the application of noise reduction measures. For each situation, we also estimated the exposure of the population and the percentages of highly annoyed and highly sleep disturbed people. We show the utility of AIS data and their specific elaboration to draw up noise abatement measures in order to reduce the noise impact on population and allow the airport development.     

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.     

Scenario analysis and noise action planning: Modelling the impact of mitigation measures on population exposure

This paper reports on strategic noise mapping research conducted in Dublin, Ireland. Noise maps are constructed for the day–evening–night-time and night-time periods and levels of population exposure are estimated for the same periods. In methodological terms, the research uses the UK’s calculation of road traffic noise (CRTN) method for calculating noise levels in the study area. This method has been adopted as the interim calculation method by the Irish authorities responsible for meeting the obligations set out in the EU Environmental Noise Directive (END). The research also investigates the usefulness of three noise mitigation measures for ‘acoustical planning’ purposes: traffic reductions, speed reductions and erection of acoustical barriers. The results indicate that levels of population exposure during night-time are extremely high relative to guideline limits set down by the World Health Organisation. In addition, the results highlight the significant role that certain noise mitigation measures can play in good ‘acoustical planning’.     

Sensitivity of the FAA Integrated Noise Model to input parameters

The standard method for computing noise contours around civil airports is SAE-AIR-1845 (FAA Integrated Noise Model, European ECAC-CEAC Doc. 29). It is subject to the inaccuracies implicit in the model as well as those caused by erroneous or imprecise input data. Regarding the latter, the existing errors and/or uncertainties, may be amplified in the output results, to a greater or lower extent, in some cases offering unreliable predictions.In order to study this phenomenon, the Institute of Sound and Vibration Research (ISVR - Southampton) carried out a theoretical sensitivity analysis based on the segmentation technique, regarding the input parameters of the SAE-AIR-1845, and obtaining the input variables of the model, the variation of which implied greater changes in the output variables. The results were validated by using the FAA Integrated Noise Model Version 6.0 software, based on the aforementioned document. It has been revealed that the model has a greater sensitivity to factors that modify the flight path, and a lower sensitivity to the other parameters. Thus, an error greater than 10% in the variable “gross weight” offers an additional error of between 3 and 7 dB. However, parameters such as the ID of the flaps hardly modify the results obtained for the least favourable case by 1 dB.As a result of this research, the sensitivity of the model was quantified for each of the input parameters (taken alone and also in interaction with other parameters), and criteria for the minimisation of global error, resulting from uncertainties in the input parameters, were stated.     

Noise mapping in urban environments: A Taiwan study

This study analyzed the spatial characteristics of urban environmental noise by using noise maps produced at 345 noise monitoring stations in Tainan, Taiwan. Noise data were collected at varying intervals: morning, afternoon, and evening in both summer and winter. The spatial distributions of the noise levels during each time interval were evaluated and visualized by geographic information systems. The analytical results indicated that the highest and lowest average noise levels were 69.6 dB(A) and 59.3 dB(A) during summer mornings and winter evenings, respectively. Comparison of monitored noise levels with regulatory standards revealed that noise standard violations, which usually occur on summer evenings, are as high as 23 dB(A). Furthermore, the results of noise exposure analysis showed that over 90% of the Tainan City population are exposed to unacceptable noise as defined by US Department of Housing and Urban Development. The findings of this study show that noise maps can be useful for investigating noise in urban environments.     

声屏障和有源噪声控制声屏障

概述了声屏障降低噪声的原理和常用方法，提出了存在的不足，介绍了有源声屏障的降噪性能与发展动态，提出了进一步研究的设想。     

Design of a reverberant chamber for noise exposure experiments with small animals

Previous work on the acoustic design of small reverberant chambers for studies on laboratory animals has paid, in general, more attention to the frequency response at certain points in their interior. These designs aimed to provide a frequency response as flat as possible at the receivers, thus avoiding unpleasant spectral coloration effects. However, an equally important, and frequently neglected, aspect is to set an acoustic field as spatially uniform as possible inside the zone where the animals are to be placed during the exposure to noise. Here, an optimization procedure is described to calculate the proportions of the chamber dimensions that confers the highest sound level with the minimum mean squared deviation averaged in a given area inside the chamber. In addition, new stimuli have been designed with a high-pass filtering and linear with frequency gain. These stimuli were intended to adapt the characteristics of the exposing noise to the rodent hearing spectrum, displaced toward higher frequencies than the hearing frequency band of humans.     

半导体激光器的噪声特性神经网络仿真

通过求解含朗之万噪声项的速率方程, 给出了噪声特性解析表达式, 建立了半导体激光器噪声特性神经网络模型. 利用该模型对噪声进行了计算机仿真, 取得了与数值计算相一致的结果. 训练好的神经网络模型具有精度高、速度快等优点.     

Statistical evaluation of occupational noise exposure

Assessment of the risk involved in occupational noise exposure (L_EP,d) is significantly affected by assumptions and uncertainties in setting true exposure conditions meaning that the calculation according to the European legislation might not be fully representative.The paper describes a probabilistic model to evaluate occupational noise exposure and calculate the confidence interval for L_EP,d. This confidence interval is defined in function of the number of samples of both exposure time and equivalent noise level that must be taken in different areas of the work environment or for different operator tasks. The model determines the minimum number and the type of samples to obtain a confidence interval for L_EP,d which falls with the given level of precision entirely into the classes defined by 86/188/CEE Directive (and following 2003/10/CE Directive).Finally, the model has been applied (by means of a software tool implementing the model and developed by the authors) to a newspaper rotary press plant, where production is supervised by a team of workers that access the various parts of the plant (3 vertical levels) for regulation and/or maintenance.     

Sound exposure during daily activities

Throughout the day people carry out different activities in different places, and are therefore exposed to a wide range of sound environments. Sound exposure does not occur uniquely in the work situation, but is also caused by non-occupational activities, such as leisure, transportation, shopping, etc.This work shows the results of a study of the sound exposure experienced by a group of 32 people during one week in the Madrid Autonomous Region in Spain. The main aim of the study is to determine the average sound exposure perceived by an inhabitant of the Madrid region; to this end the sample was designed to comprise a cross-section of the population. An analysis was made of the activities that most affect sound exposure, and of the contribution of these activities to the total sound exposure. The results obtained show that in all population groups, sound exposure is greatest on weekends. Leisure activities contribute most to the total sound received, and young adults are subjected to the highest levels of sound exposure. The results obtained in this work may be useful for local authorities in planning environmental strategies.     

Noise emission assessment of a hybrid electric mid-size truck

In the attempt to improve urban environmental conditions, city or national incentives encourage the use of cleaner vehicles, including hybrid electric vehicles. This paper explores the actual noise impact of this alternative drivetrain technology on the noise emission of a mid-size delivery truck powered by a parallel hybrid powertrain, compared with an equivalent internal combustion engine truck on the basis of pass-by noise measurements. It investigates jointly the overall emission, the main noise sources and the vertical directivity of the vehicle. The essential benefit results from the existence of a full-electric mode below 50 km/h, with a significant noise reduction which may exceed 8 dB(A) at low constant speed. Even if smaller, this noise advantage is still valuable when the vehicle is accelerating or braking. Due to weaker noise emitted upwards, the benefit should be even greater for residents living on upper building floors. The rolling noise associated with the drive wheel/road contact is the main noise source in all driving situations in electric mode, and beyond 50 km/h in the configurations with engine.     

二次JPEG压缩对噪音相关性的影响分析

为了探索二次JPEG压缩对数字图像与数码相机的噪音相关性的影响,提高利用噪音相关性鉴别数字图像来源的正确性,降低鉴别过程的复杂性,利用高品质的JPEG格式图像进行JPEG压缩实验,从噪音相关性的分布、噪音相关性的大小、鉴别阈值和错误拒绝率四个角度分析了JPEG压缩对噪音相关性的影响.实验结果表明,JPEG压缩会改变噪音相关性的分布特性,噪音相关性与品质因素是二次曲线关系,当品质因素小于90时,鉴别阈值取平均值,错误拒绝率不会产生明显的误差,从而找到了一种利用噪音相关性鉴别二次JPEG压缩图像来源的新捷径.     

基于等效电路的半导体激光器热噪音特性仿真研究

通过引入Langevin噪音项的噪音等效电路研究了半导体激光器的热噪音特性．研究表明，在激光器的工作过程中，由于自加热效应所引来的热噪音是不能够被忽略的．本文基于半导体激光器的噪音等效电路，仿真分析不同频带宽度、不同注入电流情况下，工作温度的变化对激光器结电压噪音谱的影响．     

Noise reduction by dynamic signal preemphasis

In this work we propose an approach to reduce the digitization noise for a given dynamic range, i.e., the number of bits, of an analog to digital converter used in an NMR receiver. In this approach, the receiver gain is dynamically increased so that the free induction decay is recorded in such an emphasized way that the decaying signal is digitized using as many number of bits as possible, and at the stage of data processing, the original signal profile is restored by applying the apodization that compensates the effect of the preemphasis. This approach, which we call APodization after Receiver gain InCrement during Ongoing sequence with Time (APRICOT), is performed in a solid-state system containing a pair of (13)C spins, one of which is fully isotopically labeled and the other is naturally abundant. It is demonstrated that the exceedingly smaller peak buried in the digitization noise in the conventional approach can be revealed by employing APRICOT.     

Noise and disturbance caused by vehicles crossing cattle grids: Comparison of installations

Cattle grids are used on roads and tracks to prevent grazing animals from leaving an open space without fencing onto a more controlled area where access to the road from surrounded land is more limited. They are widely used in the UK at the entrances to common and moorland areas where animals are free to roam, but also on private drive entrances. Typically, they consist of a series of metal bars across the road that are spaced so that an animal’s legs would fall through the gaps if it attempted to cross. Below the grid is a shallow pit that is intended to further deter livestock from using that particular crossing point. The sound produced as vehicles cross these devices is a characteristic low frequency “brrrr” where the dominant frequencies relates to the bar passage frequency under the tyres. The sound can be disturbing to riders and their horses and walkers and residents living close by as evidenced by press reports and the need to consider noise aspects in planning for new installations. For this reason and due to the lack of available information on the size and nature of the problem measurements and recordings have been made at a number of sites in Yorkshire in the UK. In addition, questionnaire surveys of residents living close by and façade measurements have also been used to gauge impact. Results show that there is a wide variation in the maximum noise level produced by cattle grids of apparently similar design. This can be related to impact noise produced by the movement of all or part of the grid as the frame comes under impulsive loading as the vehicle crosses. It was further established that some residents living close to the cattle grids were disturbed by the noise, and in some cases vibration, and wanted them removed or suitably modified.     

某军用机场飞机噪声暴露的模化研究

针对军用机场飞机飞行训练方式复杂多变,飞机噪声影响存在范围大、不均匀及单次事件噪声突出的特点,本文结合某军用机场实地调研测试资料,综合考察了现行评价指标对该机场飞机噪声暴露的模化效果,指出了现行指标在反映军用飞机瞬时噪声和高峰时段噪声对人的冲击影响方面的不足,提出了相应的改进措施建议,给出了高峰时段LWECPN和最大A声级LAmax两个改进指标,并分析确立了各评价指标的标准限值。最后结合调研机场的数据资料对评价指标的有效性进行了验证。论文的研究成果对军用机场飞机噪声暴露的拓展研究和通用评价指标体系的构建具有很好的参考作用。     

Noise abatement measures at airports: Contributing factors and mutual dependence

Airports are known to cause noise-related environmental concerns, mostly because significant environmental impact correlated with operation of airports arises from aircraft generated noise. In order to address this concern, many airports have applied a variety of actions that alleviate negative effects of noise i.e. noise abatement measures (NAMs). Although there are similarities between airports applying some of the NAMs, numbers and types of applied measures are quite different among them. This paper focuses on finding statistical evidence to support the hypothesis that there is a significant correlation between applied NAMs and specific characteristics related to airports. To determine the reasons why airports apply NAMs, a logistic regression method was used on the data set for 246 European airports. As predictor variables, five specific characteristics related to airports (number of runways, number of aircraft movements, distance from the city, population of the city it serves, per capita gross domestic product (GDP) of the country an airport is located in), and ten NAMs based on their mutual dependencies were used. The results demonstrate a significant correlation between the applied NAMs and particular airport-related characteristics, but also between NAMs themselves. These findings can be used to determine the likelihood of applying a particular NAM to any airport, based on the characteristics that show a significant correlation with the corresponding NAM.