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  • Transmission loss measurement of recycled granular material using wave decomposition by impulse response extraction based on deconvolution
    Železnik, Anže ...
    A simplified method for measuring transmission loss with a single fixed microphone inside an impedance tube is proposed. The separation of the incident wave from the reflected wave is achieved by ... deconvolving the loudspeaker driver voltage signal with the microphone signal to extract the impulse response. Random noise and a sinusoidal sweep signal were used as excitation signals for extraction of the impulse response, and two deconvolution methods were employed: linear deconvolution based on the adaptive LMS algorithm and simple spectral division. To avoid the overlap of incident and reflected pulses, a long impedance tube was used. Using a long impedance tube eliminates the need for an anechoic tube termination and the need to calibrate microphones. It is found that a reflective tube termination provides more accurate results compared to an approximately anechoic termination. The approximately anechoic termination shortens the available time window of the reflected pulse because it reflects some of the low-frequency sound. The standard deviation of the results and the dynamic range of the proposed method were determined experimentally. The applicability of the new method was tested on samples of unconsolidated granular material recycled from construction sites. The measured transmission losses of the different granular fractions were compared with a theoretical model for transmission losses at low frequencies. Samples consisting of smaller granule fractions were found to have surprisingly high transmission loss values. The design of the extended vertical impedance tube in combination with the proposed method is cost effective, speeds up the measurement procedure and provides reliable results.
    Source: Applied acoustics. - ISSN 0003-682X (Vol. 211, Aug. 2023, str. 1-10)
    Type of material - article, component part
    Publish date - 2023
    Language - english
    COBISS.SI-ID - 163841027

    Link(s):

    https://www.sciencedirect.com/science/article/pii/S0003682X23002967
    Repository of the University of Ljubljana – RUL
    DOI

source: Applied acoustics. - ISSN 0003-682X (Vol. 211, Aug. 2023, str. 1-10)
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