Subjective annoyance caused by indoor low-level and low frequency noise and control method

The influence of low_level noise has not been widely noticed. This paper discovered that low_level and low frequency noise(A_weighted equivalent level L eq <45 dB) causes higher probability of subjective annoyance. The fuzzy mathematic principle was applied to deal with the threshold level of subjective annoyance from noise in this study; there is preferable relationship between the indoor noise and noise annoyance at low frequency noise level. Study indicated at the same centered noise level, the change of annoyance probability is mainly caused by the change of the frequency spectrum characteristic of the indoor noise. Under low noise level environment, without change of the medium_low frequency noise, the slight increase of medium_high frequency noise level with the help of noise sheltering effect can significantly reduce the noise annoyance. This discovery brings a new resolution on how to improve the environmental quality of working or living places. A noise control model is given in this study according to the acoustic analysis.

市长电话每月综述

10月份,市长电话办公室共接听市民来话631件,其中反映占道经营、环境脏乱、市容执法人员检查走形式等市容环卫问题74件,反映偷抢骗赌、交通拥堵等公安交管问题44件,反映施工堵路等市政管理问题44件,反映噪音污染、空气污染等环境保护问题22件,反映供水、供电、供气等涉及市民日常生活的问题5l件,反映城建规划、客运服务、文教卫生、拆迁安置、工商税务、房产物业管理、劳动保障、等其他问题169件,属省级部门管理25件,市民建议7件,其它195件。一、市民建议本期市民建议7件。主要内容是:1。

Aviation environmental technology and science

Expatiating on the impact of aviation on the environment and aviation environmental protection projects are expounded, and analyzing on the atmosphere pollution and effects on the aviation noise of aircraft discharge. Researching the approach to control aircraft exhaust pollution and noise pollution, and proposing the technology and management measures to reduce air pollution.

Assessment of occupational noise pollution for metal industries in Kingdom of Saudi Arabia

The main objectives of this study was measuring levels of noise generated by machinery that workers at metal industrial facilities in the Kingdom of Saudi Arabia （KSA） are exposed to as well as to determine if these levels were in conformity with adopted standards. To achieve the objectives of this study the following six metal industrial facilities were selected： a foundry plant, a building-metal production factory, a cold processing steel manufacturing plant, a hollow-metal door and doorframe manufacturer, a car-exhaust-system factory and a metal-can producer. The study found that workers operating machinery without any kind of protection were exposed to unacceptably high levels of noise that exceeded the internationally acceptable values as per occupational noise exposure-1910.95 regulations adopted standard. It was founded that 73% of work site investigated have noise level over 85 dB. A level of 116 dB was recorded at steel plant fiat section product with continuous occupation and 115.2 dB in metal product factory with labor continuous occupation. Based on the results obtained in this study, it is evident that a competent environmental and health agency needs to be established and that stricter noise-level standards ought to be enforced in order to protect employee health.

Theoretical and experimental investigation on bridge-borne noise under moving high-speed train

Bridge-borne noise pollution caused by train-induced bridge vibration has attracted more and more attentions due to its low-frequency characteristic.In order to investigate the numerical simulation technique of bridge-borne noise and noise reduction methods,a simply supported prestressed concrete (PC) box-girder bridge is adopted for study.Based on train-track-bridge interaction theory,the dynamic response of the bridge under a moving high-speed train is calculated in time-domain and assumed as the sound source of bridge-borne noise.Then bridge-borne noise is estimated according to boundary element method (BEM) in frequency-domain.The time-frequency transform is conducted by fast Fourier transformation (FFT).The validity of the numerical simulation technique is verified through comparison with field measurement results.Furthermore,noise reduction methods are proposed and corresponding effects are discussed.Results show that the proposed numerical simulation method is feasible and accurate in assessing bridge-borne noise.The dominant frequencies of bridge vibration and bridgeborne noise range from 40 Hz to125 Hz and from 31.5 Hz to 100 Hz,respectively.The peak frequency of bridge-borne noise near the bottom plate is 63 Hz.Increasing the thickness of deck plate,adjusting the inclination of webs to 0°-12°,strengthening the boundary constraints and adding a longitudinal clapboard are very effective noise control measures.

Noise shapes the distribution pattern of an acoustic predator

Noise, an obvious effect of urbanization, has a negative impact on animal vocalizations and the hunting efficiency of acoustic predators. However, the influence of noise pollution on the spatial distribution of populations remains understudied. The aim was to assess the factors shaping the distribution pattern of an acoustic predator （long-eared owl Asio otus） in an urban-farmland matrix. We hypothesized that the probability of an acoustic predator occurring decreases with growing nocturnal noise emission. This owl survey was conducted in Krak6w （S Poland） on 79 ran- domly selected sample plots （1 km x 1 km）. Six habitat variables （area of parks, woodlands, grass- land, arable land, habitat diversity index, and noise pollution） were identified and correlated with the probability of the species＇ occurrence. Proximity to pedestrian routes and roads, habitat frag- mentation, and noise intensity was also defined at nest sites and random sites. Long-eared owls occurred on 37% of the sample plots. Occupied plots had a greater area of grassland and arable land as well as a lower level of noise pollution than the unoccupied ones. A multivariate model revealed that area of grassland and nocturnal noise emission was significantly correlated with the probability of long-eared owls occurring and that the high probability of occurrence recorded on plots with large areas of grassland was reduced by noise pollution. The noise intensity recorded at nest sites was also significantly lower than at random sites. This study suggests that apart from habitat factors, the distribution of acoustic predators in an urban matrix is driven by noise pollu- tion. This highlights the importance of proper landscape management, that is, maintaining large grassland areas and preventing noise from increasing within them.