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
Large venues and auditoriums are commonly associated with their astounding architecture. Their acoustic quality is an essential factor in its qualification as a great and functional, or a badly designed place. However, acoustics is often overlooked during the design stage of a building due to the complexity and high cost of the measurements involved. For this reason, it is important to explore more accessible ways to implement acoustics evaluations. The aim of this work is to compare typical experimental measuring methods and the use of mobile devices to assess the acoustic quality of a room. These measurements are contrasted with the software simulation of the same acoustical space. The results show that the mobile system can be used for professional measurements with low restrictions in the frequency range of interest of this study (90 Hz to 4000 Hz).
Sub-bottom profiler (SBP) is an acoustic instrument commonly used to survey underwater shallow geological structure and embedded objects whose most important performance parameter is the actual vertical resolution. This paper presented a methodology to measure and evaluate the actual vertical resolution of SBP based on an experiment in an anechoic tank, which was divided into three components: building of artificial geological model, measurement of acoustic parameters, and determination of actual vertical resolution of the acoustic profiles. First, the wedge-shaped geological model, whose thickness could be accurately controlled, was designed and built in an anechoic tank to try to directly measure the vertical resolution of SBP. Then, the acoustic pulse width of SBP was measured to calculate the theoretical general vertical resolution and extreme vertical resolution. Finally, based on the acoustic profiles obtained in the experiment, the method which was used to evaluate the actual vertical resolution by measuring the duration of reflection event was put forward. Due to comparing measurement data of different parameter settings of the SBP, the study has revealed that the SBP had the lowest resolution in the 4 kHz–500 µs setting, which was 226.5 µs, or 36.2 cm, and the highest resolution in the 15 kHz–67 µs setting, which was 72.7 µs, or 11.6 cm. The vertical resolution decreased with the increase of the pulse width. The results also showed that the actual resolution was close to the theoretical general resolution and far from the extreme resolution.
The paper discusses acoustic problems in the contemporary Catholic church, and presents a study of the influence of the ceiling structure on acoustics in the interior for two types of ceiling structures, i.e. the truss type and the reinforced concrete one. The investigations involved six contemporary churches: three buildings with a truss type ceiling and three buildings with a reinforced concrete ceiling. The results reveal that in churches with a truss type ceiling, acoustic parameters reach values close to recommendations. In contrast, churches with a concrete ceiling create very unfavourable acoustic conditions. The investigations rendered it possible to calculate the sound absorption coefficient α for the truss type cover.
The paper analyzes the monthly day equivalent levels, Lday (06–22 h) and night equivalent levels, Lnight (22–06 h) values observed in year 2015 and 2016 for the 70 locations whereby continuous noise monitoring is conducted under the National Ambient Noise Monitoring Network (NANMN). The study exclusively analyzes the ambient noise data acquired for 25 locations in commercial zone, 12 in industrial, 16 in residential and 17 in silence zones. The analysis of (Lday–Lnight) for 70 locations under observations reveals that 10 dB night time adjustment in day-night average sound level descriptor is not appropriate in such a scenario and as such it is recommended to use day-night average sound level and day-eveningnight average sound level descriptors without any 10 dB night time adjustment or 5 dB evening time adjustments. The analysis and conclusions of the present study shall be very useful for developing single value noise descriptor correlating the noise annoyance and health effects in Indian perspectives.