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    Wyświetlanie 1-3 z 3
    Tytuł:
    Reflection and Transmission of Plane Wave at an Interface Between Two Rotating Micropolar Piezoelectric Solid Half-Spaces
    Autorzy:
    Singh, Baljeet
    Sangwan, Asha
    Singh, Jagdish
    Powiązania:
    https://bibliotekanauki.pl/articles/2141703.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    plane wave
    micropolar piezoelectricity
    reflection and transmission
    amplitude ratios
    energy ratios
    rotation
    Opis:
    In this paper, we investigate a problem on reflection and transmission of plane-waves at an interface between two dissimilar half-spaces of a transversely isotropic micropolar piezoelectric material. The entire model is assumed to rotate with a uniform angular velocity. The governing equations of rotating and transversely isotropic micropolar piezoelectric medium are specialized in a plane. Plane-wave solutions of two-dimensional coupled governing equations show the possible propagation of three coupled plane-waves. For an incident plane-wave at an interface between two dissimilar half-spaces, three reflected and three transmitted waves propagate with distinct speeds. The connections between the amplitude ratios of reflected and transmitted waves are obtained. The expressions for the energy ratios of reflected and transmitted waves are also obtained. A numerical example of the present model is considered to illustrate the effects of rotation on the speeds and energy ratios graphically.
    Źródło:
    Archives of Acoustics; 2021, 46, 4; 623-635
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparison of Two Types of Combined Measures, STI and U50, for Predicting Speech Intelligibility in Classrooms
    Autorzy:
    Choi, Y.-J.
    Powiązania:
    https://bibliotekanauki.pl/articles/176560.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    speech intelligibility
    speech transmission index
    useful-to-detrimental sound ratios
    classrooms
    Opis:
    The present study reports on the speech intelligibility as measured by speech transmission index (STI) and useful-to-detrimental sound ratios (U50) in university classrooms. Acoustic measurements were made in 12 quietly occupied university classrooms. The measured impulse responses of the classrooms were used to determine the modulation transfer function, m(F), for the STI calculation according to IEC 60268-16. U50 values were determined from both signal-to-noise ratios (SNR) and C50 values. The mean STI and frequency-weighted U50 values for the 12 occupied classrooms were strongly linearly related. The results showed that classrooms with U50 values of about +0.5 dB correspond to STI values of 0.60, indicating ‘good’ acoustical conditions for speech intelligibility. The results illustrate that the U50 measure can be a more practically useful means of assessing and understanding room acoustics conditions for real speech communication in active classrooms.
    Źródło:
    Archives of Acoustics; 2017, 42, 3; 527-532
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Novel Method for Determining Optimum Dimension Ratios for Small Rectangular Rooms
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177897.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    room acoustics
    small room
    optimum dimension ratios
    room impulse response
    frequency room response
    Opis:
    A new method for determining optimum dimension ratios for small rectangular rooms has been presented. In a theoretical model, an exact description of the room impulse response was used. Based on the impulse response, a frequency response of a room was calculated to find changes in the sound pressure level over the frequency range 20-200 Hz. These changes depend on the source and receiver positions, thus, a new metric equivalent to an average frequency response was introduced to quantify the overall sound pressure variation within the room for a selected source position. A numerical procedure was employed to seek a minimum value of the deviation of the sound pressure level response from a smooth fitted response determined by the quadratic polynomial regression. The most smooth frequency responses were obtained when the source was located at one of the eight corners of a room. Thus, to find the best possible dimension ratios, in the numerical procedure the optimal source position was assumed. Calculation results have shown that optimum dimension ratios depend on the room volume and the sound damping inside a room, and for small and medium volumes these ratios are roughly 1 : 1.48 : 2.12, 1 : 1.4 : 1.89 and 1 : 1.2 : 1.45. When the room volume was suitably large, the ratio 1 : 1.2 : 1.44 was found to be the best one.
    Źródło:
    Archives of Acoustics; 2018, 43, 2; 217-225
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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