Measurements have been carried out to determine the effect of porous sediments in a pipe on the attenuation and spectrum of the airborne acoustic field. The results show that the presence of even a relatively thin sandy layer results in a considerable increase in the acoustic attenuation over the broad frequency range. The measured value of the relative attenuation is in the range of 0.6 dB/m. The effect of the sediment on the acoustic spectrum is the reduction in energy of the propagating modes, which is an easily detectable phenomenon. These results pave the way for the development of the instrumentation for non-invasive characterisation of the parameters of sediments in wastewater systems.

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