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Number of results: 15
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Abstract

Amplitude modulation increases the annoyance caused by wind turbine noise. One gets the improved annoyance when a penalty is added to the measured or calculated time-average sound level. The amplitude modulated wind turbine noise consists of pulses. Each of them could be characterized by the short timeaverage sound level and the modulation depth. The latter determines the pulse penalty. This paper shows how to calculate the improved annoyance of amplitude modulated wind turbine noise, when the short time-average sound level and the penalty for each pulse are known. A special case of identical pulses is discussed. The proposed methodology needs to be tested by research.
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Authors and Affiliations

Rufin Makarewicz
1

  1. Chair of Acoustics, Faculty of Physics, Adam Mickiewicz University, Poznan, Poland
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Abstract

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

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Authors and Affiliations

Tadeusz Wszołek
Paweł Pawlik
Dominik Mleczko
Jagna Chronowska
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Abstract

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).

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Authors and Affiliations

David Ibarra-Zarate
Ana Laura Padilla-Ortiz
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Abstract

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.

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Authors and Affiliations

Fangqi Wang
Lifeng Dong
Jisheng Ding
Xinghua Zhou
Changfei Tao
Xubo Lin
Guanhui Liang
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Abstract

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.

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Authors and Affiliations

Anna Sygulska
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Abstract

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.

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Authors and Affiliations

Naveen Garg
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Abstract

For the purpose of reducing the impact noise transmission across floating floors in residential buildings, two main sound transmission paths in the floating floor structure are considered: the stud path and the cavity path. The sound transmission of each path is analysed separately: the sound transmission through the cavity and the stud are predicted by statistical energy analysis (SEA). Then, the sound insulation prediction model of the floating floor is established. There is reasonable agreement between the theoretical prediction and measurement, and the results show that a resilient layer with low stiffness can attenuate the sound bridge effect, resulting in higher impact noise insulation. Then, the influences of the floor covering, the resilient layer and the floor plate on the impact sound insulation are investigated to achieve the optimised structure of the floating floor based on the sound insulation.
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Authors and Affiliations

Xianfeng Huang
1 2
Yimin Lu
3
Chen Qu
1
Chenhui Zhu
1

  1. College of Civil Engineering and Architecture, Guangxi University, Nanning 530004, China
  2. Guangxi Key Laboratory of Disaster Prevention and Engineering Safety, Guangxi University, Nanning 530004, China
  3. School of Electrical Engineering, Guangxi University, Nanning 530004, China
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Abstract

Voice controlled management systems are based on speech recognition techniques. The use of such systems in combat aircraft is complex due to a number of critical factors which affect the accuracy of speech recognition, such as high level of ambient noise and vibration, use of oxygen masks, serious psycho-physical stress of speakers, etc. One of the specificity of the oxygen mask application is overpressure breathing. The results of the simulations presented in this paper show that the presence of overpressure on the order of 1000 Pa in the vocal tract has a significant influence on the first two formant frequencies. The formants discrimination field is significantly reduced when oxygen mask is used, influencing both perceptive and automatic discrimination of spoken vowels.
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Authors and Affiliations

Milan Vojnović
1
Miomir Mijić
2
Dragana Šumarac Pavlović
2
Nebojša Vojnović
2

  1. Life Activities Advancement Center, Belgrade, Serbia
  2. University of Belgrade, School of Electrical Engineering, Belgrade, Serbia
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Abstract

In this paper, a four-pole system matrix for evaluating acoustic performance (STL) is derived using a decoupled numerical method. During the optimization process, a simulated annealing (SA) method, which is a robust scheme utilized to search for the global optimum by imitating a physical annealing process, is used. Prior to dealing with a broadband noise, to recheck the SA method’s reliability, the STL’s maximization relative to a one-tone noise (400Hz) is performed. To assure the accuracy of muffler’s mathematical model, a theoretical analysis of one-diffuser muffler is also confirmed by an experimental data. Subsequently, the optimal results of three kinds of mufflers (muffler A: one diffuser; muffler B: two diffusers; muffler C: three diffusers) have also been compared. Results reveal that the acoustical performance of mufflers will increase when the number of diffusers installed at the muffler inlet increases
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Bibliography

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2. Chang Y.C., Yeh L.J., Chiu M.C. (2004), Numerical studies on constrained venting system with side inlet/outlet mufflers by GA optimization, Acta Acustica united with Acustica, 90(6): 1159–1169.
3. Chang Y.C., Yeh L.J., Chiu M.C. (2005a), Shape optimization on double-chamber mufflers using genetic algorithm, Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 219(1): 31–42, doi: 10.1243/095440605X8351.
4. Chang Y.C., Yeh L.J., Chiu M.C., Lai G.J. (2005b), Shape optimization on constrained singlelayer sound absorber by using GA method and mathematical gradient methods, Journal of Sound and Vibration, 1286(4–5): 941–961, doi: 10.1016/j.jsv.2004.10.039.
5. Chiu M.C. (2009a), Optimization of equipment allocation and sound-barriers shape in a multi-noise plant by using simulated annealing, Noise & Vibration Worldwide, 40(7): 23–35, doi: 10.1260/095745609788921857.
6. Chiu M.C. (2009b), Simulated annealing optimization on multi-chamber mufflers hybridized with perforated plug-inlet under space constraints, Archives of Acoustics, 34(3): 305–343.
7. Chiu M.C. (2010a), Numerical optimization of a threechamber muffler hybridized with a side inlet and a perforated tube by SA method, Journal of Marine Science and Technology, 18(4): 484–495, doi: 10.51400/2709-6998.1897.
8. Chiu M.C. (2010b), Optimal design of multi-chamber mufflers hybridized with perforated intruding inlets and resonated tube using simulated annealing, Journal of Vibration and Acoustics, 132(5): Article ID 054503, doi: 10.1115/1.4001514.
9. Chiu M.C. (2012), Noise elimination of a multi-tone broadband noise with hybrid Helmholtz mufflers using a simulated annealing method, Archives of Acoustics, 37(4): 489–498, doi: 10.2478/v10168-012-0061-0.
10. Chiu M.C. (2013), Numerical assessment for a broadband and tuned noise using hybrid mufflers and a simulated annealing method, Journal of Sound and Vibration, 332(12): 2923–2940, doi: 10.1016/j.jsv.2012.12.039.
11. Chiu M.C. (2014a), Acoustical treatment of multi-tone broadband noise with hybrid side-branched mufflers using a simulated annealing method, Journal of Low Frequency Noise Vibration and Active Control, 33(1): 79–112, doi: 10.1260/0263-0923.33.1.79.
12. Chiu M.C. (2014b), Optimal design on one-layer closefitting acoustical hoods using a simulated annealing method, Journal of Marine Science and Technology, 22(2): 211–217, doi: 10.6119/JMST-013-0503-1.
13. Chiu M.C., Chang Y.C. (2014), An assessment of high-order-mode analysis and shape optimization of expansion chamber mufflers, Archives of Acoustics, 39(4): 489–499, doi: 10.2478/aoa-2014-0053.
14. Kirkpatrick S., Gelatt C.D., Vecchi M.P. (1983), Optimization by simulated annealing, Science, 220 (4598): 671–680, doi: 10.1126/science.220.4598.671.
15. Metropolis A., Rosenbluth W., Rosenbluth M.N., Teller H., Teller E. (1953), Equation of static calculations by fast computing machines, The Journal of Chemical Physics, 21(6): 1087–1092, doi: 10.1063/1.1699114.
16. Munjal M.L. (1987), Acoustics of Ducts and Mufflers with Application to Exhaust and Ventilation System Design, John Wiley & Sons, New York.
17. Munjal M.L., Rao K.N., Sahasrabudhe A.D. (1987), Aeroacoustic analysis of perforated muffler components, Journal of Sound and Vibration, 114(2): 173– 188, doi: 10.1016/S0022-460X(87)80146-3.
18. Peat K.S. (1988), A numerical decoupling analysis of perforated pipe silencer elements, Journal of Sound and Vibration, 123(2), 199–212.
19. Sullivan J.W. (1979a), A method of modeling perforated tube muffler components I: theory, The Journal of the Acoustic Society of America, 66(3): 772–778, doi: 10.1121/1.383679.
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Authors and Affiliations

Min-Chie Chiu
1
Ho-Chih Cheng
2

  1. Department of Mechanical and Materials Engineering, Tatung University, Taiwan, R.O.C.
  2. Department of Intelligent Automation Engineering, Chung Chou University of Science and Technology, Taiwan, R.O.C.
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Abstract

At the beginning of the COVID-19 pandemic the government of Spain decreed the State of Alarm to confine the entire population at their homes, except for essential services. Therefore, the central objective of this study is to evaluate the implication of this situation for the environmental noise existing in the city of Huelva (Spain). This study demonstrates that during the state of alarm an average daily reduction of 3.4 dBA was noted, and in the central moments of the day these reductions reached up to 4.4 dBA, while from 10:00 to 12:00 pm the reduction was around 6.5 dBA. Nevertheless, there were two moments of day: 3:00 am (garbage collection, street cleaning and container disinfection), and 8:00 pm (daily applause for health professionals), when the noise during the pandemic was higher than before it. It is further shown that globally, the loudest events only decreased by about 3 dBA, while the global background noise decreased by 10 dBA during the alarm state. Regarding road traffic noise, it is verified that in addition to being reduced by about 4 dBA, traffic represents 6.7% of noisy events during the alarm state, while before it represented 13%.
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Authors and Affiliations

Juan Carlos Fortes
1
Rafael Sánchez-Sánchez
1
Juan Pedro Bolívar
2

  1. School of Engineering, University of Huelva, Huelva, Spain
  2. Faculty of Experimental Sciences, University of Huelva, Huelva, Spain
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Abstract

Using intelligent materials and sensors to monitor the safety of concrete structures is a hot topic in the field of civil engineering. In order to realize the omni-directional monitoring of concrete structural damage, the authors of this paper designed and fabricated an embedded annular piezoelectric ultrasonic sensor using the annular piezoelectric lead zirconate titanate (PZT) ceramic as a sensing element and epoxy resin as the matching and the backing layers. The influence of different matching and backing layers thickness on the acoustic characteristic parameters of the sensor were studied. The results show that the resonant frequency corresponding to the axial mode of annular piezoelectric ceramics moves toward the high frequency direction with the decrease of the height of piezoelectric ceramics, and the radial vibration mode increases as well as the impedance peak. With the thickness of the backing layer increases from 1 mm to 2 mm, the radial resolution of the annular piezoelectric ultrasonic sensor is enhanced, the pulse width is reduced by 39% comparing with the sensors which backing layer is 1 mm, and the head wave amplitude and −3 dB bandwidth are increased by 61% and 66%, respectively. When the matching layer thickness is 3 mm, the sensor has the highest amplitude response of 269 mV and higher sensitivity.
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Authors and Affiliations

Haoran Li
1
Yan Hu
2
Laibo Li
1
Dongyu Xu
2 3

  1. Shandong Provincial Key Lab of Preparation and Measurement of Building Materials, University of Jinan, Jinan 250022, PR China
  2. School of Civil Engineering, Central South University, Changsha 410075, PR China
  3. School of Civil Engineering and Architecture, Linyi University, Linyi 276000, PR China
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Abstract

Noise is unwanted sound judged to be unpleasant, loud or disruptive to hearing. Like air pollution, noise pollution is one of the serious matters of concern in urban areas. Noise pollution occurs when noise level exceeds certain limit and has deleterious effects on human health and wellness. The major sources of noise pollution are industries, road traffic, railways, airplane traffic and social celebrations. The traffic noise is notably high in cities due to higher density of population, frequent movement of people, good transport system coupled with increasing numbers of vehicles (on road). In this work, the assessments of traffic noise in Sambalpur city is presented. Twelve important locations were chosen for the assessment. Noise contours were drawn to visualize the spreading of traffic noise into its surroundings. At the same time, the effect of noise pollution on wellness of the exposed people was studied. The study shows that the traffic noise level and its effects, are both in an alarming stage in the city.
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Authors and Affiliations

Alekh Kumar Sahu
1
Satish Kumar Nayak
2
Chitta Ranjan Mohanty
3
Prasant Kumar Pradhan
1

  1. Department of Mechanical Engineering, Veer Surendra Sai University of Technology, Burla, India
  2. Department of Civil Engineering, Veer Surendra Sai University of Technology, Burla, India
  3. Department of Civil Engineering, Parala Maharaja Engineering College, Berhampur, India
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Abstract

The presence of noises in the vehicle cabin is an annoyance phenomenon which is significantly affected by the heating, ventilation, and air conditioning (HVAC) system. There are very limited studies reported on the specific type of noise characterisation and validation for both model and vehicle system levels. The present study developed a model of HVAC system that reflects the operation as in real vehicle, and the investigation of the HVAC components were carried out individually to determine which component contributes to the humming-type noise and vibration. The study was conducted under two conditions; idle speed of engine (850 rpm) and operating condition (850–1400 rpm). A ixed blower speed and fullface setting were applied throughout the experimental process. Three different sensors were used for the experiment, which are: accelerometer, tachometer, and microphone. From the results, the compressor and AC pipe components have contributed the most in generating the noise and vibration for both the model and vehicle systems. The findings also highlight that the humming-type noise and vibration were produced in the same operating frequency of 300–400 Hz and 100–300 Hz for idle and operating conditions, respectively, and this result was validated for both model and vehicle system levels.
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Authors and Affiliations

Mohd Hafiz Abdul Satar
1
Ahmad Zhafran Ahmad Mazlan
1
Muhd Hidayat Hamdan
1
Mohd Syazwan Md Isa
1
Muhd Abdul Rahman Paiman
2
Mohd Zukhairi Abd Ghapar
2

  1. The Vibration Lab, School of Mechanical Engineering, Universiti Sains Malaysia 14300 Nibong Tebal, Penang, Malaysia
  2. Testing & Development, Vehicle Development & Engineering, Proton Holdings Berhad, 40000 Shah Alam, Selangor, Malaysia
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Abstract

Heating, ventilation and air conditional (HVAC) system provides a cold ventilation for the comfort of the driver and passengers in a vehicle. However, the vibration induced by the HVAC contributes to a reasonable level of noise emission, and hissing is one of the critical noises. So far, the characterization of hissing noise from the vehicle is least to be reported compared to other type of noises. Hence, this paper investigates the occurrence of hissing noise from several HVAC components. A lab-scale HVAC system was developed to imitate the real-time operations of the vehicle HVAC system. Two engine conditions, namely as ambient and operating conditions, were tested at speed of 850 rpm and 850–1400 rpm, with the blower speed maintained constantly at one level. The result shows that the hissing noise from the labscale HVAC was produced at frequency range of 4000–6000 Hz. The finding also highlights that the main component contributors of noise emission are an evaporator and a thermal expansion valve. The validation with a real vehicle system showed a good consensus whereby the hissing noise was produced at the similar operating frequency ranges. Also, the hissing noise was found to be louder when in an operating condition which could be taken into consideration by the vehicle manufacturers to improve the HVAC design.
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Authors and Affiliations

Mohd Hafiz Abdul Satar
1
Ahmad Zhafran Ahmad Mazlan
1
Muhd Hidayat Hamdan
1
Mohd Syazwan Md Isa
1
Muhd Abdul Rahman Paiman
2
Mohd Zukhairi Abd Ghapar
2

  1. The Vibration Lab, School of Mechanical Engineering, Universiti Sains Malaysia 14300 Nibong Tebal, Penang, Malaysia
  2. Testing & Development, Vehicle Development & Engineering, Proton Holdings Berhad, 40000 Shah Alam, Selangor, Malaysia

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