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    Wyświetlanie 1-9 z 9
    Tytuł:
    Speech Enhancement Using Sliding Window Empirical Mode Decomposition and Hurst-based Technique
    Autorzy:
    Poovarasan, Selvaraj
    Chandra, Eswaran
    Powiązania:
    https://bibliotekanauki.pl/articles/176311.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    speech enhancement
    Empirical Mode Decomposition
    EMD
    Intrinsic Mode Functions
    hurst exponent
    Sliding Window
    SW
    Opis:
    The most challenging in speech enhancement technique is tracking non-stationary noises for long speech segments and low Signal-to-Noise Ratio (SNR). Different speech enhancement techniques have been proposed but, those techniques were inaccurate in tracking highly non-stationary noises. As a result, Empirical Mode Decomposition and Hurst-based (EMDH) approach is proposed to enhance the signals corrupted by non-stationary acoustic noises. Hurst exponent statistics was adopted for identifying and selecting the set of Intrinsic Mode Functions (IMF) that are most affected by the noise components. Moreover, the speech signal was reconstructed by considering the least corrupted IMF. Though it increases SNR, the time and resource consumption were high. Also, it requires a significant improvement under nonstationary noise scenario. Hence, in this article, EMDH approach is enhanced by using Sliding Window (SW) technique. In this SWEMDH approach, the computation of EMD is performed based on the small and sliding window along with the time axis. The sliding window depends on the signal frequency band. The possible discontinuities in IMF between windows are prevented by the total number of modes and the number of sifting iterations that should be set a priori. For each module, the number of lifting iterations is determined by decomposition of many signal windows by standard algorithm and calculating the average number of sifting steps for each module. Based on this approach, the time complexity is reduced significantly with suitable quality of decomposition. Finally, the experimental results show the considerable improvements in speech enhancement under non-stationary noise environments.
    Źródło:
    Archives of Acoustics; 2019, 44, 3; 429-437
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of Pipe Bends on the Low-Frequency Torsional Guided Wave Propagation
    Autorzy:
    Wu, Wenjun
    Wang, Junhua
    Powiązania:
    https://bibliotekanauki.pl/articles/176823.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    guided wave
    torsional mode
    pipe bends
    mode conversion
    Opis:
    Wave motion in pipe bends is much more complicated than that in straight pipes, thereby changing considerably the propagation characteristics of guided waves in pipes with bends. Therefore, a better understanding of how guided waves propagate in pipe bends is essential for inspecting pipelines with bends. The interaction between a pipe bend and the most used non-dispersive torsional mode at low frequency in a small-bore pipe is studied in this paper. Experiments are conducted on a magnetostrictive system, and it is observed that T(0,1) bend reflections and mode conversions from T(0,1) to F(1,1) and F(2,1) occur in the pipe bend. The magnitude of the T(0,1) bend reflections increases with increasing propagation distance and excitation frequency. The amplitude of the mode-converted signals also increases with increasing propagation distance, but it decreases with increasing excitation frequency. Because of their longer bent path, the test signals for a pipe bend with a bending angle of 180º are much more complicated than those for one with a bending angle of 90º. Therefore, it is even more difficult to scan a bent pipe with a large bending angle. The present findings provide some insights into how guided waves behave in pipe bends, and they generalize the application of guided-wave inspection in pipelines.
    Źródło:
    Archives of Acoustics; 2020, 45, 3; 385-391
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Correction of Evanescent Wave Influence on the Flexural Wave Velocity and Wavelength Estimation Based on a Mode Shape Function
    Autorzy:
    Pantelić, Filip
    Šumarac Pavlović, Dragana
    Mijić, Miomir
    Ridley-Ellis, Daniel
    Powiązania:
    https://bibliotekanauki.pl/articles/31339954.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    mode shape function
    flexural wave velocity
    very near field
    Opis:
    The aim of this research is to use a simple acoustic method of a very near field recording, which enables measurement and display of oscillation modes, to estimate the velocity of flexural waves, based on the wavelengths of standing waves measured on the sample. The paper analyses cases of 1D geometry, flexural waves that occur on a beam excited by an impulse. Measurements were conducted on two different samples: steel and a wooden beam of the same length. Due to the appearance of evanescent waves at the boundary regions, the distance between the nodes of standing waves that occur deviates from half the wavelength, which can be compensated using a correction factor. Cases of fixed and free boundary conditions were analysed. By quantifying how much the boundary conditions change the mode shape function, it can be predicted how the mode of oscillation changes if the boundary conditions change, which can also find application in musical acoustics and sound radiation analysis.
    Źródło:
    Archives of Acoustics; 2022, 47, 4; 539-546
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Radiation of Sound Waves by a Semi-Infinite Duct with Outer Lining and Perforated End
    Autorzy:
    Tiryakioglu, Burhan
    Powiązania:
    https://bibliotekanauki.pl/articles/177688.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    Wiener-Hopf
    mode matching
    perforated end
    duct
    radiation
    Opis:
    Radiation of sound waves from a semi-infinite cylindrical duct with perforated end whose outer wall is coated with acoustically absorbent material is investigated by using the Wiener-Hopf technique in conjunction with the mode matching technique. A semi-infinite duct with a perforated screen can be used as a model for many engineering applications, such as noise reduction in exhausts of automobile engines, in modern aircraft jet, and turbofan engines. In particular, we aim to find the effects of outer lining and perforated end to sound pressure level for the underlying problem by using the standard Wiener-Hopf and mode matching techniques. We also present some numerical illustrations by determining the sound pressure level for different parameters such as soft and rigid outer surface, with and without perforated end, etc. Such investigations are useful in the reduction of noise effects generated through variety of sources.
    Źródło:
    Archives of Acoustics; 2020, 45, 1; 77-84
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    VMD and CNN-Based Classification Model for Infrasound Signal
    Autorzy:
    Lu, Quanbo
    Li, Mei
    Powiązania:
    https://bibliotekanauki.pl/articles/31339812.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    infrasound signal
    variational mode decomposition
    convolutional neural network
    Fast Fourier Transform
    Opis:
    Infrasound signal classification is vital in geological hazard monitoring systems. The traditional classification approach extracts the features and classifies the infrasound events. However, due to the manual feature extraction, its classification performance is not satisfactory. To deal with this problem, this paper presents a classification model based on variational mode decomposition (VMD) and convolutional neural network (CNN). Firstly, the infrasound signal is processed by VMD to eliminate the noise. Then fast Fourier transform (FFT) is applied to convert the reconstructed signal into a frequency domain image. Finally, a CNN model is established to automatically extract the features and classify the infrasound signals. The experimental results show that the classification accuracy of the proposed classification model is higher than the other model by nearly 5%. Therefore, the proposed approach has excellent robustness under noisy environments and huge potential in geophysical monitoring.
    Źródło:
    Archives of Acoustics; 2023, 48, 3; 403-412
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analysis of the Influencing Factors of the Acoustic Performance of the Muffler Considering Acoustic-structural Coupling
    Autorzy:
    Zhao, Bo
    Li, He
    Powiązania:
    https://bibliotekanauki.pl/articles/31339942.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    acoustic performance
    muffler
    acoustic-structural coupling
    transmission loss
    mode
    optimisation
    Opis:
    In the calculation of the acoustic performance of mufflers, the walls of mufflers are usually treated rigidly without considering the acoustic-structural coupling, but the results so calculated differ significantly from the actual situation. Based on the basic equations, the article derives the finite element equations of the muffler system while considering the acoustic-structural coupling effect and theoretically analyses the connection between the acoustic-structural coupling system and the structural and acoustic modes. The structural and acoustic modes of the muffler are calculated and the reasons for the mutation of the transmission loss curve of the muffler when the acoustic-structural coupling is considered are analysed. The results show that the acoustic-structural coupling is the result of the interaction between the structure and the air inside the expansion chamber under acoustic excitation, which manifests mutations in the sound pressure inside the muffler in some frequency bands. Then, using a single-chamber muffler as an example, the transmission loss is used to characterise the performance of the muffler. The effects of different factors such as shell thickness, structure, porous media material lining, and restraint method on the acoustic-structural coupling effect of the muffler are analysed, and the structure of a double-chamber muffler is successfully optimised according to the conclusions.
    Źródło:
    Archives of Acoustics; 2022, 47, 4; 479-490
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An Improved EMD Method Based on Utilizing Certain Inflection Points in the Construction of Envelope Curves
    Autorzy:
    Kafil, Mohsen
    Darabi, Kaveh
    Ziaei-Rad, Saeed
    Powiązania:
    https://bibliotekanauki.pl/articles/31339815.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    empirical mode decomposition
    EMD
    interpolation points
    envelope curve
    inflection points
    rolling element bearing fault diagnosis
    Opis:
    The empirical mode decomposition (EMD) algorithm is widely used as an adaptive time-frequency analysis method to decompose nonlinear and non-stationary signals into sets of intrinsic mode functions (IMFs). In the traditional EMD, the lower and upper envelopes should interpolate the minimum and maximum points of the signal, respectively. In this paper, an improved EMD method is proposed based on the new interpolation points, which are special inflection points (SIPn) of the signal. These points are identified in the signal and its first (n − 1) derivatives and are considered as auxiliary interpolation points in addition to the extrema. Therefore, the upper and lower envelopes should not only pass through the extrema but also these SIPn sets of points. By adding each set of SIPi (i = 1, 2, n) to the interpolation points, the frequency resolution of EMD is improved to a certain extent. The effectiveness of the proposed SIPn-EMD is validated by the decomposition of synthetic and experimental bearing vibration signals.
    Źródło:
    Archives of Acoustics; 2023, 48, 3; 389-401
    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:
    Normal Mode Solutions of Target Strengths of Solid-filled Spherical Shells and Discussion of Influence Parameters
    Autorzy:
    Jia, Bing
    Fan, Jun
    Li, Gui-Juan
    Wang, Bin
    Chen, Yun-Fei
    Powiązania:
    https://bibliotekanauki.pl/articles/31339751.pdf
    Data publikacji:
    2024
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    solid-filled spherical shell
    room temperature vulcanized silicone rubber
    target strength enhancement
    Opis:
    The normal mode solution for the form function and target strength (TS) of a solid-filled spherical shell is derived. The calculation results of the spherical shell’s acoustic TS are in good agreement with the results of the finite element method (FEM). Based on these normal mode solutions, the influences of parameters such as the material, radius, and thickness of the inner and outer shells on the TS of a solid-filled spherical shell are analyzed. An underwater spherical shell scatterer is designed, which uses room temperature vulcanized (RTV) silicone rubber as a solid filling material and does not contain a suspension structure inside. The scatterer has a good TS enhancement effect.
    Źródło:
    Archives of Acoustics; 2024, 49, 1; 83-93
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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