The assessment of teachers' exposure to noise in primary schools was carried out on the basis of: questionnaire studies (covering 187 teachers in 3 schools), noise measurements at the teachers' workplaces, measurements of the school rooms acoustic properties (reverberation time and speech transmission index STI in 72 classrooms), analysis of statistical data regarding hazards and occupational diseases in the education sector. The studies have shown that noise is the main factor of annoyance in the school environment. Over 50% of questioned teachers consider noise as annoying and near 40% as very annoying or unbearable. A-weighted equivalent continuous sound pressure levels measured in classrooms, teacher rooms and common rooms are in the range of 58-80 dB and they exceed 55 dB (criteria of noise annoyance). The most frequently reported subjective feelings and complaints (over 90%) are: growth of psychical and emotional tension, irritation, difficulties in concentrating, hoarseness, cough. Noise in schools is also a harmful factor. High A-weighted equivalent continuous sound pressure levels ranging from 80 to 85 dB, measured in corridors during pauses and in sports halls, can cause the risk of hearing damage among PE teachers and persons oversensitive to noise. The latter concerns both teachers and pupils. High background noise levels (55-65 dB) force teachers to raise their voice. It can lead to the development of an occupational disease - chronic voice disorders due to excessive vocal effort lasting for at least 15 years. In the education sector 785 new cases of this disease were reported only in 2008. Poor acoustics in classrooms (reverberation time ranging from 0.8 to 1.7 s, STI < 0.6 in 50% of classrooms) have an adverse influence on speech reception and make the teaching and learning processes difficult.

The specific working conditions of the wind turbine in strong wind cause a number of problems in the measurement of noise indicators used in its short and long-term assessment. The wind is a natural working environment of the turbine, but it also affects the measurement system, moreover, it can be a secondary source of other sounds that interfere with the measurement. One of the effective methods of eliminating the direct impact of wind on the measurement system is placing the microphone on the measurement board at ground level. However, the obtained result can not be directly compared with the admissible values, as it has to be converted to a result at a height of 4 m. The results of previous studies show that this relation depends, inter alia, on the speed and direction of the wind. The paper contains the results of measurements on the measurement board, according to EN 61400-11:2013, and at a height of 4 m above ground made simultaneously in three points around the 2 MW turbine at various instantaneous speeds and changing wind directions. Analysis of the impact of measuring point location on the measurement result of noise indicators and the occurrence of additional features affecting the relationship between the values measured on the board and at the height of 4 m, and especially the tonality, amplitude modulation and content of low frequency content, was m

The acoustic vector sensor (AVS) is used to measure the acoustic intensity, which gives the direction-ofarrival (DOA) of an acoustic source. However, while estimating the DOA from the measured acoustic intensity the finite microphone separation (d) in a practical AVS causes angular bias. Also, in the presence of noise there exists a trade off between the bias (strictly increasing function of d) and variance (strictly decreasing function of d) of the DOA estimate. In this paper, we propose a novel method for mitigating the angular bias caused due to finite microphone separation in an AVS. We have reduced the variance by increasing the microphone separation and then removed the bias with the proposed bias model. Our approach employs the finite element method (FEM) and curves fitting to model the angular bias in terms of microphone separations and frequency of a narrowband signal. Further, the bias correction algorithm based on the intensity spectrum has been proposed to improve the DOA estimation accuracy of a broadband signal. Simulation results demonstrate that the proposed bias correction scheme significantly reduces the angular bias and improves the root mean square angular error (RMSAE) in the presence of noise. Experiments have been performed in an acoustic full anechoic room to corroborate the effect of microphone separation on DOA estimation and the efficacy of the bias correction method.