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    Wyświetlanie 1-13 z 13
    Tytuł:
    Low Frequency Noise and Its Assessment and Evaluation
    Autorzy:
    Žiaran, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/176925.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    low frequency sound
    human being
    health
    evaluation
    Opis:
    The main aim of this paper is to present recent knowledge about the assessment and evaluation of low frequency noise and infrasound close to the threshold of hearing and the potential effects on human health. Low frequency noise generated by air flowing over a moving car with the open window is chosen as a source of noise. The noise within the interior of the car and its effects on a driver’s comfort at different velocities is analyzed. An open window at high velocity behaves as a source of specifically strong tonal low frequency noise which is annoying. The interior noise of a passenger car was measured under different conditions; while driving on normal highway and roadways. First, an octave-band analysis was used to assess the noise level and its impact on the driver’s comfort. Second, a Fast Fourier Transform (FFT) analysis was used for the detection of tonal low frequency noise. Finally, the paper suggests possibilities for scientifically assessing and evaluating low frequency noise but not only for the presented source of the sound.
    Źródło:
    Archives of Acoustics; 2013, 38, 2; 265-270
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Brain’s Frequency Following Responses to Low-Frequency and Infrasound
    Autorzy:
    Jurado, Carlos
    Marquardt, Torsten
    Powiązania:
    https://bibliotekanauki.pl/articles/176507.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    low-frequency hearing
    frequency-following response
    infrasound
    auditory brain
    Opis:
    Complaints and awareness about environmental low-frequency (LF) noise and infrasound (IS) have increased in recent years, but knowledge about perceptual mechanisms is limited. To evaluate the use of the brain’s frequency-following response (FFR) as an objective correlate of individual sensitivity to IS and LF, we recorded the FFR to monaurally presented IS (11 Hz) and LF (38 Hz) tones over a 30-phon range for 11 subjects. It was found that 11-Hz FFRs were often significant already at ~0 phon, steeply grew to 20 phon, and saturated above. In contrast, the 38-Hz FFR growth was relatively shallow and continued to 60 phon. Furthermore, at the same loudness level (30 phon), the 11-Hz FFR strength was significantly larger (4.5 dB) than for 38 Hz, possibly reflecting a higher phase synchronization across the auditory pathway. Overall, unexpected inter-individual variability as well as qualitative differences between the measured FFR growth functions and typical loudness growth make interpretation of the FFR as objective correlate of IS and LF sensitivity difficult.
    Źródło:
    Archives of Acoustics; 2020, 45, 2; 313-319
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electrical Characterization of 65 W Cubic Sonoreactor with Horizontally Stacked Transducers
    Autorzy:
    Kerdthongmee, P.
    Pholnak, C.
    Sirisathitkul, C.
    Danworaphong, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/176328.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    sonoreactor
    dual stack transducer
    low frequency ultrasound
    RLC circuit
    resonant frequency
    Opis:
    A sonoreactor was assembled with stacked lead zirconate titanate transducers. These transducers were attached on one side of a 10×10×10 cm3 chamber and driven by an integrated circuit power amplifier. The impedance of the reactor was analyzed in order to determine a matching inductance. The electrical frequency could be varied from 20 to 50 kHz and the electrical output power was adjustable up to 65 W. The highest power was obtained in the case of resonance at 31 kHz and the maximum temperature at the heat sink of the amplifier rose to 42.0ºC. Both acoustic cavitation and mechanical effects could be utilized in this sonoreactor for a variety of purposes including sonochemical synthesis, ultrasonic cleaning and microbial cell disruption.
    Źródło:
    Archives of Acoustics; 2017, 42, 1; 149-153
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Study on Chinese Speech Intelligibility Under Different Low-Frequency Characteristics of Reverberation Time Using a Hybrid Method
    Autorzy:
    Huang, Wuqiong
    Peng, Jianxin
    Xie, Tinghui
    Powiązania:
    https://bibliotekanauki.pl/articles/31339871.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    low frequency
    speech intelligibility
    classroom
    finite-difference time-domain method
    Opis:
    Reverberation time (RT) is an important indicator of room acoustics, however, most studies focus on the mid-high frequency RT, and less on the low-frequency RT. In this paper, a hybrid approach based on geometric and wave methods was proposed to build a more accurate and wide frequency-band room acoustic impulse response. This hybrid method utilized the finite-difference time-domain (FDTD) method modeling at low frequencies and the Odeon simulation at mid-high frequencies, which was investigated in a university classroom. The influence of the low-frequency RT on speech intelligibility was explored. For the low-frequency part, different impedance boundary conditions were employed and the effectiveness of the hybrid method has also been verified. From the results of objective acoustical parameters and subjective listening experiments, the smaller the low-frequency RT was, the higher the Chinese speech intelligibility score was. The syllables, consonants, vowels, and the syllable order also had significant effects on the intelligibility score.
    Źródło:
    Archives of Acoustics; 2023, 48, 3; 151-157
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Study and Assessment of Low Frequency Noise in Occupational Settings
    Autorzy:
    Shehap, A. M.
    Shawky, H. A.
    El-Basheer, T. M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177844.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    low frequency noise
    A-weighting
    C-weighting
    audible
    method of assessment
    Opis:
    Low frequency noise is one of the most harmful factors occurring in human working and living environment. Low frequency noise components from 20 to 250 Hz are often the cause of employee complaints. Noise from power stations is an actual problem for large cities, including Cairo. The noise from equipments of station could be a serious problem for station and for environmental area. The development of power stations in Cairo leads to appearing a wide range of gas turbines which are strong source of noise. Two measurement techniques using C-weighted along side the A-weighted scale are explored. C-weighting is far more sensitive to detect low frequency sound. Spectrum analysis in the low frequency range is done in order to identify a significant tonal component. Field studies were supported by a questionnaire to determine whether sociological or other factors might influence the results by using annoyance rating mean value. Subjects included in the study were 153 (mean = 36.86, SD = 8.49) male employees at the three electrical power stations. The (C-A) level difference is an appropriate metric for indicating a potential low frequency noise problem. A-weighting characteristics seem to be able to predict quite accurately annoyance experienced from LFN at workplaces. The aim of the present study is to find simple and reliable method for assessing low frequency noise in occupational environment to prevent its effects on work performance for the workers. The proposed method has to be compared with European methods.
    Źródło:
    Archives of Acoustics; 2016, 41, 1; 151-160
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Acoustic Study of REpower MM92 Wind Turbines During Exploitation
    Autorzy:
    Kłaczyński, M.
    Wszołek, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/177881.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    wind turbine noise
    low frequency noise
    airfoil self noise
    measurements assessment
    Opis:
    The paper presents the current state of knowledge concerning the sources of noise generated by wind turbines, force measurement methodology, and assessment of noise onerousness in this type of installation, on the basis of a study concerning a wind farm with five REpower MM92 wind turbines and the electric power of 2 MW and the sound power level of 104.2 dB(A) each. Particular attention was focused on the often discussed problem of presence of infrasound generated by turbines and on the requirements of the applicable reference methodologies for the measurement of wind speed to 5 m/s, while the turbine reaches its full power at speeds above 10 m/s.
    Źródło:
    Archives of Acoustics; 2014, 39, 1; 3-10
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An Improved MSA Model for Evaluating the Sound Transmission Loss of a Rectangular Plate for Diffuse Field Incidence
    Autorzy:
    Kim, Myong-Jin
    Won, Kyong-Su
    Ri, Chol-Su
    Powiązania:
    https://bibliotekanauki.pl/articles/176309.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    transmission loss
    low frequency range
    natural vibration mode
    diffuse field incidence
    Opis:
    This paper presents an approximate analytical model for estimating the transmission loss (TL) of a finite rectangular plate in the low frequency range, which is based on the modal summation approach (MSA) taking into account the modal radiation impedance and fluid loading. The mode-dependent radiation resistance is calculated using the Rayleigh integral. The fluid loading is taken into account through the natural frequency modified by the added mass. The results are compared with the ones of Statistical Energy Analysis (SEA) coupled with FEM and FEM coupled with BEM. In addition, the effects of the various vibration modes and the fluid loading on TL, and a way for reducing the calculation time are discussed.
    Źródło:
    Archives of Acoustics; 2019, 44, 2; 259-265
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of a Geometrical-Stiffening Membrane Acoustic Metamaterial with Individually Tunable Multi-Frequencies
    Autorzy:
    Zhao, Junjuan
    Li, Xianhui
    Thompson, David
    Wang, Yueyue
    Wang, Wenjiang
    Zhu, Liying
    Liu, Yunan
    Powiązania:
    https://bibliotekanauki.pl/articles/1953515.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    membrane acoustic metamaterial
    nonlinear geometric stiffening
    low frequency tuning
    sound transmission
    Opis:
    To realize a structure which can be conveniently tuned to multiple and wideband frequency ranges, a geometrical-stiffening membrane acoustic metamaterial (MAM) with individually tunable multiple frequencies is presented. The MAM is realized by a stacked arrangement of two membrane-magnet elements, each of which has a membrane with a small piece of steel attached in the centre. It can be tuned individually by adjusting the position of its compact magnet. The normal incidence sound transmission loss of the MAM is investigated in detail by measurements in an impedance tube. The test sample results demonstrate that this structure can easily achieve a transmission loss with two peaks which can be shifted individually in a wide low-frequency range. A theoretical consideration is analysed, the analysis shows that the magnetic effect related to this distance leads to a nonlinear attractive force and, consequently, nonlinear geometrical stiffening in each membrane-magnet element, which allows the peaks to be shifted. A reasonable design can make the structure have a good application prospect for low-frequency noise insulation where there is a need to adjust the transmission loss according to the spectrum of the noise source.
    Źródło:
    Archives of Acoustics; 2021, 46, 1; 87-93
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Measurement of Compound Sound Sources with Adaptive Spatial Radiation for Low-Frequency Active Noise Control Applications
    Autorzy:
    Giouvanakis, Marios
    Sevastiadis, Christos
    Papanikolaou, George
    Powiązania:
    https://bibliotekanauki.pl/articles/1953496.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    Low-Bl loudspeakers
    compound sound sources
    adaptive spatial radiation
    active low-frequency noise control
    Opis:
    The proposed compound sound sources for low-frequency noise control applications are composed of dipole sources. Their spatial radiation, which is critical in the modal field of small, closed spaces, is intended to be controlled with independent driving signals of each dipole. The need for small and efficient low-frequency elementary monopole sources led to the proposed vented sub-woofer loudspeaker design with low force factor (low-Bl) drivers. The investigated sources are set up in quadrupole configurations and measured in terms of polar near field response patterns to verify the theoretical predictions. The measurement results consist of the validation of the proposed compound sound sources on the implementation of active noise control problems in the low-frequency range. Also, their small size and modular construction make them interesting for use in other applications.
    Źródło:
    Archives of Acoustics; 2021, 46, 2; 205-212
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Noise Control Transmission Methods of the Combustion Engine by Means of Reduction of the Vibration
    Autorzy:
    Žiaran, S.
    Chlebo, O.
    Powiązania:
    https://bibliotekanauki.pl/articles/176754.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    combustion engine
    low frequency waves
    transmission
    health
    measures
    silnik spalinowy
    fale niskiej częstotliwości
    skrzynia biegów
    zdrowie
    środki
    Opis:
    Transmission of vibroacoustic energy from an internal combustion engine (ICE) to its surroundings largely depends on how it is mounted, on available transmission paths and on the construction of the vehicle body and/or its surrounding structures. This is especially true in low speed engines in enclosed areas which generate perceptually weak noise, but strong low-frequency waves which energy has a negative impact on human health, comfort and driving safety especially in prolonged exposure to the source. The primary aim of the article was to analyse components of the ICE unit which had a determining impact on the reduction of low-frequency waves. Thus, the structurally transmitted noise from the ICE to its surrounding structure (body of the passenger vehicle) was analysed. The results of the vibroacoustic measurements were compared to modal analysis in order to determine possible resonance sources in the vehicle body and/or for assessing the influence of the vehicles safety gear on the generated vibroacoustic energy transfer into the cabin area of the passenger vehicle. Measurements were made for a passenger vehicle at rest and operating in its most common operational speed as well as for the stationary ICE of a cogenerate unit (CGU). Measurements and FFT analysis were used for the detection of the vibroacoustic energy sound pressure level (noise) and mechanical vibration. Firstly, the low-frequency noise sources were determined and their direct effects on the human body were investigated. Finally, this paper suggests some measures which may contribute to the reduction of undesirable vibroacoustic energy in enclosed areas.
    Źródło:
    Archives of Acoustics; 2016, 41, 2; 277-284
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Low-Frequency Sound Absorption Potential of Subwavelength Absorbers Based on Coupled Micro-Slit Panels
    Autorzy:
    Qian, Yujie
    Gao, Zhengyuan
    Zhang, Jie
    Powiązania:
    https://bibliotekanauki.pl/articles/31339748.pdf
    Data publikacji:
    2024
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    coupled MSP
    CMSP
    cavity-depth optimal scheme COS
    panel thickness optimal scheme TOS
    low frequency
    absorption performance
    Opis:
    Due to space limitations during installation, reducing low-frequency noise has always been a challenging area. Sub-wavelength structures are typically favored in such scenarios for noise reduction. This paper explores the potential of micro-slit panels (MSP) for low-frequency sound absorption. To further optimize the panel thickness, coupled MSPs (CMSP) with a distance between two MSPs of less than 1 mm are proposed. Firstly, the low-frequency absorption performances of a single MSP based on two optimized schemes – the cavity-depth optimal scheme (COS) and the panel thickness optimal scheme (TOS) – are examined and compared with those of existing ultrathin metamaterials. The results demonstrate that MSP has significant potential for low frequency sound absorption, and COS allows for a smaller overall structural thickness but a larger panel thickness than TOS. Secondly, to reduce the panel thickness, the CMSP is developed and the theoretical model of its acoustic impedance is established and validated by experiments. Then, based on the theoretical model, the low-frequency absorption potential of CMSP is optimized using COS. The results show that both the overall thickness and the panel thickness of the CMSP absorber are reduced while maintaining better performance. Furthermore, the proposed absorber achieves a subwavelength scale since its total thickness can be as small as 0.138λ.
    Źródło:
    Archives of Acoustics; 2024, 49, 1; 121-128
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Design Sensitivity Studies on a Hydroacoustic Projector Using an Experimentally Validated Easy-to-Build Model
    Autorzy:
    Sreejith, Vattaparambil Sreedharan
    Tiwari, Nachiketa
    Powiązania:
    https://bibliotekanauki.pl/articles/2141678.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    low frequency sound source
    underwater transducer
    fluid power
    hydro-electro-mechano-acoustic analogy
    hydraulic valve
    piston
    cylinder
    Opis:
    Hydroacoustic projectors are useful for generating low frequency sounds in water. Existing works on hydroacoustic projectors require two significant enhancements, especially for designers. First, we need to understand the influence of important projector design parameters on its performance. Such insights can be very useful in developing a compact and efficient projector. Second, there is a need for an integrated model of the projector based on easily available and user-friendly numerical tools which do not require development of complex customised mathematical analogs of projector components. The present work addresses both such needs. Towards these goals, an experimentally validated, easy-to-build projector model was developed and used to conduct design sensitivity studies. We show that reductions in pipe compliance and air content in oil, and an increase in orifice discharge coefficient can yield remarkable improvements in projector’s SPL. We also show that reductions in pipe length and cylinder diameter cause moderate improvements in performance in mass and stiffness controlled regions, respectively. In contrast, the projector performance is insensitive to changes in pistonic mass, cylinder length, and diaphragm stiffness. Finally, we report that while pipe compliance and air content in oil can sharply alter system resonance, the effects of changes in pipe length and pistonic mass on it are moderate in nature.
    Źródło:
    Archives of Acoustics; 2022, 47, 1; 113-124
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Experimental Study of Identifying Emission Sources of Acoustic Signals on the Cylinder Body of a Two-Stroke Marine Diesel Engine
    Autorzy:
    Dong, Xuan Thin
    Nguyen, Manh Hung
    Powiązania:
    https://bibliotekanauki.pl/articles/1953513.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    acoustic emission
    two-stroke marine diesel engine
    experimental method
    low-to-high frequency ranges
    medium-to-high frequency ranges
    vibration
    Opis:
    In this paper, an experimental method was utilized to investigate acoustic emission (AE) characteristics and to identify emission sources of the nonlinear AE signal on the cylinder body of a large low-speed two-stroke marine diesel engine in real-working conditions on the sea in misfiring and normal firing modes. Measurements focused on the AE signal acquired in a transverse direction in low-frequency (20-80 kHz), medium-frequency (100-400 kHz) and high-frequency (400-900 kHz) ranges. The collected signals were analyzed on the crank angle and crank angle-frequency domains. The results showed that all potential sources of the nonlinear AE signal could be mapped in the low-frequency range. However, only the AE signal caused by the combustion process at around the top dead center could be well-observed in the medium-to-high-frequency range. The findings also revealed that in normal firing conditions, the AE energy radiated by friction in the down-stroke period was smaller than in the up-stroke process due to gas-sealing forces. Moreover, the AE energy in the misfiring condition was higher than in the normal firing state. These outcomes considerably contributed understandings to characteristics of friction and wear around the mid-stroke area of the cylinder on a two-stroke marine diesel engine.
    Źródło:
    Archives of Acoustics; 2021, 46, 1; 105-119
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-13 z 13

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