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Wyświetlanie 1-15 z 18
Tytuł:
Effects of Acoustic Treatment on Music Teachers’ Exposure to Sound
Autorzy:
Kozłowski, E.
Młyński, R.
Powiązania:
https://bibliotekanauki.pl/articles/177728.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
music teachers
sound pressure level
acoustic treatment
Opis:
In this study, music teachers’ exposure to sound was tested by measuring the A-weighted equivalent sound pressure level (SPL), the A-weighted maximum SPL and the C-weighted peak SPL. Measurements were taken prior to and after acoustic treatment in four rooms during classes of trumpet, saxophone, French horn, trombone and percussion instruments. Results showed that acoustic treatment affects the exposure of music teachers to sound. Daily noise exposure levels (LEX, 8 h) for all teachers exceeded a limit of 85 dB while teaching music lessons prior to room treatment. It was found that the LEX, 8 h values ranged from 85.8 to 91.6 dB. The highest A-weighted maximum SPL and C-weighted peak SPL that music teachers were exposed to were observed with percussion instruments (LAmax = 110.4 dB and LCpeak = 138.0 dB). After the treatments, daily noise exposure level decreased by an average of 5.8, 3.2, 3.0, 4.2 and 4.5 dB, respectively, for the classes of trumpet, saxophone, French horn, trombone and drums, and did not exceed 85 dB in any case.
Źródło:
Archives of Acoustics; 2014, 39, 2; 159-163
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sound Radiation by a Cylindrical Open Cavity with a Surface Source at the Bottom
Autorzy:
Szemela, K.
Powiązania:
https://bibliotekanauki.pl/articles/176682.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
open cylindrical cavity
sound pressure
sound power
continuity conditions
Opis:
The rigorous solution describing the sound radiation by an arbitrary surface source located at the bottom of a cylindrical open cavity embedded in a flat baffle has been obtained. The open cavities of different shapes can be found in some architectural structures as well as are components of sensors, musical instruments and vehicles. The presented formulas have been expressed in the form of Infinite sums. To use them, the infinite sums have to be truncated to the finite number of terms. Therefore, in practice, the results obtain based on the proposed solution are not exact and their accuracy is determined by the truncation error. The use of presented formulas is an alternative method for the finite element method (FEM). However, taking into account that the calculation efficiency of FEM rapidly decrease when a volume of considered region increases, the obtained in this study solution can be more useful in some practical cases. The approximated formula of a high computational efficiency has been presented for the sound pressure in the far field. The sound radiation has been analyzed for a rectangular piston as a sound source. The influence of cavity depth ratio on the radiation efficiency has been investigated. The cases for which the cavity radiation efficiency can be approximately calculated from the formula valid for a baffled sound source have been determined.
Źródło:
Archives of Acoustics; 2018, 43, 1; 49-60
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on Noise Attenuation Characteristics of Hydrofoil with Specific Cavitation Number
Autorzy:
Xiaohui, He
Zhongle, Liu
Chao, Yang
Zhiyong, Yuan
Powiązania:
https://bibliotekanauki.pl/articles/31339799.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
sound pressure spectrum
noise
sound power spectrum
numerical prediction
Opis:
In this study, the modified Sauer cavitation model and Kirchhoff-Ffowcs Williams and Hawkings (K-FWH) acoustic model were adopted to numerically simulate the unsteady cavitation flow field and the noise of a three-dimensional NACA66 hydrofoil at a constant cavitation number. The aim of the study is to conduct and analyze the noise performance of a hydrofoil and also determine the characteristics of the sound pressure spectrum, sound power spectrum, and noise changes at different monitoring points. The noise change, sound pressure spectrum, and power spectrum characteristics were estimated at different monitoring points, such as the suction side, pressure side, and tail of the hydrofoil. The noise characteristics and change law of the NACA66 hydrofoil under a constant cavitation number are presented. The results show that hydrofoil cavitation takes on a certain degree of pulsation and periodicity. Under the condition of a constant cavitation number, as the attack angle increases, the cavitation area of the hydrofoil becomes longer and thicker, and the initial position of cavitation moves forward. When the inflow velocity increases, the cavitation noise and the cavitation area change more drastically and have a superposition tendency toward the downstream. The novelty is that the study presents important calculations and analyses regarding the noise performance of a hydrofoil, characteristics of the sound pressure spectrum, and sound power spectrum and noise changes at different monitoring points. The article may be useful for specialists in the field of engineering and physics.
Źródło:
Archives of Acoustics; 2023, 48, 3; 359-372
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Technical Possibilities of Reducing the Sound Pressure Level Emitted into the Environment by a Power Transformer
Autorzy:
Borucki, S.
Boczar, T.
Cichoń, A.
Powiązania:
https://bibliotekanauki.pl/articles/177473.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
power transformer
corrected sound pressure level
noise
modernization
Opis:
The subject presented in this paper refers to measurements and assessment of the corrected sound pressure level values (noise) occurring around a medium-power transformer. The paper presents the values of noise accompanying the operation of the power object before and after its modernization, which consisted in repeated core pressing and replacement of the cooling system. The main aim of the research work was the assessment of the influence of the repair work on the noise level emitted into the environment.
Źródło:
Archives of Acoustics; 2011, 36, 1; 49-56
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis and Optimization of Micro Speaker-Box Using a Passive Radiator in Portable Device
Autorzy:
Jiang, Y.-W.
Kwon, J.-H.
Kim, H.-K.
Hwang, S.-M.
Powiązania:
https://bibliotekanauki.pl/articles/176530.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
passive radiator
speaker box
SPL improvement
Sound Pressure Level
Opis:
With the rapid development of multimedia devices such as smart phones and tablet PCs, microspeakers have been recently increasingly used for audio equipment. Improving the acoustic performance of a microspeaker is always a main concern, especially in the low frequency range. To avoid sound cancelation, a microspeaker unit is usually inserted into a speaker box. A passive radiator is also used in speaker boxes to improve the sound performance in the loudspeaker system. However, passive radiators have not been applied into microspeaker system. In this study, a speaker box with a passive radiator was analyzed and optimized to achieve a higher Sound Pressure Level (SPL) in a microspeaker system. The Finite Element Method (FEM), two-degree-of-freedom (DOF) vibration theory, and a plane circular piston sound source were used to study the electromagnetic, vibration, and acoustic characteristics, respectively. Optimization was conducted by changing the mass, stiffness, and size of the passive radiator. Based on the optimized parameters, a new sample was manufactured. The experiment results show that the SPL of the optimized speaker box with a passive radiator is improved by 5 dB at 200 Hz compared with the one without a radiator. The analysis results also matched the experiment results.
Źródło:
Archives of Acoustics; 2017, 42, 4; 753-760
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Fast Method of Feature Extraction for Lowering Vehicle Pass-By Noise Based on Nonnegative Tucker3 Decomposition
Autorzy:
Wang, H.
Cheng, G.
Deng, G.
Li, X.
Li, H.
Huang, Y.
Powiązania:
https://bibliotekanauki.pl/articles/177883.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
vehicle pass-by noise
NTD
feature extraction
sound pressure level
Opis:
Usually, the judgement of one type fault of vehicle pass-by noise is difficult for engineers, especially when some significant features are disturbed by other interference noise, such as the squealing noise is almost simultaneous with the whistle in the exhaust system. In order to cope with this problem, a new method, with the antinoise ability of the algorithm on the condition by which the features are entangled, is developed to extract clear features for the fault analysis. In the proposed method, the nonnegative Tucker3 decomposition (NTD) with fast updating algorithm, signed as NTD_FUP, can find out the natural frequency of the parts/components from the exhaust system. Not only does the NTD_FUP extract clear features from the confused noise, but also it is superior to the traditional methods in practice. Then, an aluminium-foil alloy material, which is used for the heat shield for its lower noise radiation, replaces the aluminium alloy alone. Extensive experiments show that the sound pressure level of the vehicle pass-by noise is reduced 0.9 dB(A) by the improved heat shield, which is also considered as a more lightweight design for the exhaust system of an automobile.
Źródło:
Archives of Acoustics; 2017, 42, 4; 619-629
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Overview of the Noise Levels Measured in Industrial Facilities in Serbia and Implemented Methods of Protection
Autorzy:
Luburić, Uranija Kozmidis
Samardžić, Selena
Lakatoš, Robert
Mihailović, Aleksandra
Veselinović, Milka
Powiązania:
https://bibliotekanauki.pl/articles/176762.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
noise
industry
SPL
sound pressure level
frequency analysis
noise protection
Opis:
Noise is one of the most significant factors which not only disturbs working conditions, but has a large impact on workers’ health. This problem has existed in industries since the beginning and, despite technical and other solutions, it has not been solved. There is a large number of papers, supported with very detailed analyses, that investigate noise levels in industry or contain questionnaires about the impact of noise on workers’ overall health and work abilities. The purpose of this paper is to contribute to the global picture of sustainability and the development of strategies for improving the quality of working environment, with special attention to the generation of noise in different production processes in thirteen different industries in Novi Sad, Serbia. The paper also seeks to examine the advantages and drawbacks of the implemented protective methods and to provide some recommendations for their better implementation in order to contribute to solving this significant problem of today.
Źródło:
Archives of Acoustics; 2020, 45, 3; 499-510
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Urethane Foam Cushioning on Structure-Borne Sound Transfer by a Slab with Panel Flooring
Autorzy:
Mu, R.
Toyoda, M.
Takahashi, D.
Powiązania:
https://bibliotekanauki.pl/articles/176817.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
urethane foam
direct pasted flooring
floor impact sound
sound pressure level
sound insulation performance
Opis:
Urethane foam mattresses are commonly used as cushioning when placing panel flooring on the floor slab of a building. Urethane foam consists of elastic fibres with pores. Both elements can affect the performance of the insulation against impact sounds. However, these effects have not yet been detailed, and they may change if the material properties or constitution of the fibres and pores in the cushioning change. In this paper, we propose an analytical model for use in evaluating the performance of insulation against floor impact sound. This model was used to examine the contribution of the pores versus the elastic fibres to wave transmissions from the flooring surface to the slab. The results reveal that the constitution of the foam (either open or closed cells of pores) and the thickness and hardness of the cushion layer strongly affect the sound insulation performance of the floor.
Źródło:
Archives of Acoustics; 2016, 41, 1; 99-106
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acoustic Analysis Using Sound Level Meter to Determine the Period of Usage of the Spindle Bearing of a Radial Drilling Machine
Autorzy:
Charles, S.
Vijaya, Joslin D.
Powiązania:
https://bibliotekanauki.pl/articles/176769.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
acoustical condition monitoring
radial drilling machine
spindle bearing
sound level meter
sound pressure level
sound muting transducer
Opis:
The condition monitoring techniques like acoustic emission, vibration analysis, and infrared thermography, used for the failure diagnosis of bearings, require longer processing time, as they have to per form acoustical measurement followed by signal processing and further analysis using special software. However, for any bearing, its period of usage can be easily determined within an hour, by measuring the bearing sound, using sound level meter (SLM). In this paper the acoustical analysis of the spindle Bering of a radial drilling machine was performed using SLM, by measuring the sound pressure level of the bearing in decibels, for different frequencies, while muting all the other noises. Then using an experimental set up, two database readings were taken, one for new bearing and the other for completely damaged bearing, both are SKF6207, which itself is the spindle bearing. From these three sets of sound pressure level readings, the period of usage of the spindle bearing, was calculated using an interpolation equation, by substituting the life of the bearing from the manufacturer’s catalogue. Therefore, for any machine with a SKF6207 bearing, its usage time can be estimated using the database readings and one measurement on that machine, all with the same speed.
Źródło:
Archives of Acoustics; 2019, 44, 3; 505-510
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sound Radiation from a Surface Source Located at the Bottom of the Wedge Region
Autorzy:
Szemela, K.
Powiązania:
https://bibliotekanauki.pl/articles/176912.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
wedge region
sound pressure
sound power
Neumann boundary value problem
Helmholtz equation
vibrating piston
Hankel transform
Opis:
Applying rigorous analytical methods, formulas describing the sound radiation have been obtained for the wedge region bounded by two transverse baffles with a common edge and bottom. It has been assumed that the surface sound source is located at the bottom. The presented formulas can be used to calculate the sound pressure and power inside the wedge region. They are valid for any value of the wedge angle and represent a generalization of the formulas describing the sound radiation inside the two and three-wall corner region. Moreover, the presented formulas can be easily adapted for any case when more than one sound source is located at the bottom. To demonstrate their practical application, the distribution of the sound pressure modulus and the sound power have been analyzed in the case of a rectangular piston located at the wedge’s bottom. The influence of the transverse baffle on the sound power has been investigated. Based on the obtained formulas, the behaviour of acoustic fields inside a wedge can be predicted.
Źródło:
Archives of Acoustics; 2015, 40, 2; 223-234
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
3D Multi-Domain MFS Analysis of Sound Pressure Level Reduction Between Connected Enclosures
Autorzy:
Godinho, L.
Branco, F. G.
Mendes P., A.
Powiązania:
https://bibliotekanauki.pl/articles/177013.pdf
Data publikacji:
2011
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Method of Fundamental Solutions (MFS)
domain decomposition
closed spaces
sound pressure level reduction
Opis:
In this paper, the authors study the 3D propagation of sound waves between two closed spaces. The separation element between the two rooms is considered to include either a small opening or a homogeneous lightweight panel, coupling the two spaces. A numerical study of this configuration is performed, trying to understand the influence of the position and geometry of this opening in the sound pressure level reduction curve at low and midfrequencies. Additionally, the coupling effect between the two acoustic spaces is analyzed, in order to better understand its importance when determining the sound pressure level reduction. Different boundary conditions are ascribed to the walls of these rooms, simulating both the completely reflecting and partially absorbing surfaces. The numerical modelling was performed using a multi-domain formulation of the Method of Fundamental Solutions (MFS). The system is composed of two coupled rooms, limited by rigid or by absorbing walls, and separated by a thin wall (tending to null thickness) with a small opening. An experimental validation of the proposed model is presented, comparing its results with those found experimentally for a reduced-scale model. It is important to note that, for such a configuration, a traditional single-domain approach using methods like the MFS or the BEM would lead to undetermined equation systems, and thus the proposed model makes use of a domain decomposition technique.
Źródło:
Archives of Acoustics; 2011, 36, 3; 575-601
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analytical and Computational Acoustic Modelling of Side Outlet Muffler and Its Extension in the Modelling of Tapered Side Outlet Muffler
Autorzy:
Vishwakarma, Sandeep Kumar
Pawar, Jayappa
Powiązania:
https://bibliotekanauki.pl/articles/31339955.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
1-D analysis
finite element analysis
FEA
sound pressure level
transfer matrix
transmission loss
Opis:
Mufflers are popular in the suppression of noise levels coming from various machinery. The most common parameters for the evaluation of the performance of mufflers are transmission loss, noise level, and insertion loss. The transmission loss is evaluated for tapered side outlet muffler using finite element analysis without considering the fluid-structure interaction. This study includes analytical modelling and acoustic modelling of the side outlet muffler and transmission loss is in excellent agreement with the reference paper. The feasibility of the acoustic model is also verified with the experimental work on simple expansion chamber muffler. The same finite element analysis is extended for the tapered side outlet muffler. The transmission loss of the tapered side outlet muffler in the given frequency range is found 8.96 dB better than the side outlet muffler. The acoustic pressure level and sound pressure level contours for the tapered side outlet muffler give a clear picture of wave propagation inside the muffler. The effect of the cut-off frequency on the transmission loss of the tapered side outlet muffler can be seen from the contours. This study can be helpful in the determination of the performance of the mufflers in terms of transmission loss, the performance of mufflers above cut-off frequency, and design improvements in the muffler to avoid the higher-order modes of the sound wave.
Źródło:
Archives of Acoustics; 2022, 47, 4; 491-499
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Relationship Between Chinese Speech Intelligibility of Elderly and Speech Transmission Index
Autorzy:
Peng, Jianxin
Zeng, Jiazhong
Zhao, Yuezhe
Powiązania:
https://bibliotekanauki.pl/articles/1953494.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
speech intelligibility
speech transmission index
signal-to-noise ratio
background noise level
speech sound pressure level
reverberation time
Opis:
In this paper, the relationship between Chinese speech intelligibility (CSI) scores of the elderly aged 60-69 and over 70 years old, and speech transmission index (STI) were investigated through the auralization method under different reverberation time and background noise levels (BNL, 40 dBA and 55 dBA). The results show that the CSI scores of the elderly are significantly worse than those of young adults. For the elderly over 70, the CSI scores become much lower than those of young adults. To be able to achieve the same CSI, the elderly, especially those over 70, need much higher STI and greater SNR than the young. The elderly aged 60-69 and over 70 need to improve their STI by 0.419 and 0.058 respectively under BNL 40 dBA, as well as 0.282 and 0.072 respectively under BNL 55 dBA, so as to obtain the same CSI scores as the young adults.
Źródło:
Archives of Acoustics; 2021, 46, 2; 229-235
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evaluation and Analysis of Environmental Noise Pollution in Seven Major Cities of India
Autorzy:
Garg, N.
Sinha, A. K.
Dahiya, M.
Gandhi, V.
Bhardwaj, R. M.
Akolkar, A. B.
Powiązania:
https://bibliotekanauki.pl/articles/177396.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
NANMN
National Ambient Noise Monitoring Network
day equivalent level
Lday
night equivalent level
Lnight
day-night average sound level
Ldn
equivalent continuous sound pressure level
LAeq,24h
Opis:
The paper describes the noise monitoring data acquired from the pilot project on the establishment of National Ambient Noise Monitoring Network (NANMN) across seven major cities in India for continuous noise monitoring throughout the year. The annual average Lday (06–22 h) and Lnight (22–06 h) values observed in year 2011–2014 for the 35 locations under study in which 14 locations are in commercial zone, 5 in Industrial, 7 in residential and 9 in silence zones are described. The long-term noise monitoring shows that ambient noise levels have marginally increased for 29 sites (82.9%) since past four years. The present study is focused on evaluation and analysis of environmental noise pollution at 35 noise monitoring sites in seven major cities of India and shall be instrumental in planning for the noise abatement measures for controlling the noise pollution in these sites.
Źródło:
Archives of Acoustics; 2017, 42, 2; 175-188
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acoustic Nonlinearity Parameter B/A, Internal Pressure, and Acoustic Impedance Determined at Pressures up to 100 MPa for 1-Ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide
Autorzy:
Zorębski, E.
Zorębski, M.
Dzida, M.
Powiązania:
https://bibliotekanauki.pl/articles/177585.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nonlinearity parameter
speed of sound
high pressure
ionic liquids
internal pressure
Opis:
The nonlinearity parameter B/A, internal pressure, and acoustic impedance are calculated for a room temperature ionic liquid, i.e. for 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide for temperatures from (288.15 to 318.15) K and pressures up to 100 MPa. The B/A calculations are made by means of a thermodynamic method. The decrease of B/A values with the increasing pressure is observed. At the same time B/A is temperature independent in the range studied. The results are compared with corresponding data for organic molecular liquids. The isotherms of internal pressure cross at pressure in the vicinity of 70 MPa, i.e. in this range the internal pressure is temperature independent.
Źródło:
Archives of Acoustics; 2016, 41, 1; 59-66
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 18

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