Article:Duan, W., Kirby, R., Prisutova, J. et al.(1 more author) (2015) On the use of power reflection ratio and phase change to determine the geometry of a blockage in a pipe. Applied Acoustics, https://doi.org/10.1016/j.apacoust.2014.07.002 eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. 1On the use of power reflection ratio and phase change to determine the geometry of a blockage in a pipe the echo from the blockage. This presents a fast and efficient way of determining the presence of a blockage and this method is now being used, for example, to probe the integrity of sewer systems. In this article a method is presented for obtaining both the length and the equivalent cross-sectional area of a blockage using only a single microphone to capture the incident and reflected pulse. The method presented uses the change in phase between the incident and reflected acoustic signals caused by a blockage, as well as the difference in the amplitude of each pulse, to generate two independent equations from which the area ratio and the length of the blockage may be recovered. This requires measurements to be carried out in the plane wave region of the pipe, however it is shown that through appropriate processing of each signal in the frequency domain the area ratio and length of a relatively large number of blockages can be successfully recovered.

Acoustic intensity is normally treated as a real quantity, but in recent years many articles have appeared in which intensity is treated as a complex quantity where the real (active) part is related to local mean energy flow, and the imaginary (reactive) part to local oscillatory transport of energy. This offers the potential to recover additional information about a sound field and then to relate this to the properties of the sound source and the environment that surrounds it. However, this approach is applicable only to a multi-modal sound fields, which places significant demands on the accuracy of the intensity measurements. Accordingly, this article investigates the accuracy of complex intensity measurements obtained using a tri-axial Microflown intensity probe by comparing measurement and prediction for sound propagation in an open flanged pipe. Under plane wave conditions comparison between prediction and experiment reveals good agreement, but when a higher order mode is present the reactive intensity field becomes complicated and agreement is less successful. It is concluded that the potential application of complex intensity as a diagnostic tool is limited by difficulties in measuring reactive intensity in complex sound fields when using current state of the art acoustic instrumentation.3

The measurement of acoustic material characteristics using a standard impedance tube method is generally limited to the plane wave regime below the tube cut-on frequency. This implies that the size of the tube and, consequently, the size of the material specimen must remain smaller than a half of the wavelength. This paper presents a method that enables the extension of the frequency range beyond the plane wave regime by at least a factor of 3, so that the size of the material specimen can be much larger than the wavelength. The proposed method is based on measuring of the sound pressure at different axial locations and applying the spatial Fourier transform. A normal mode decomposition approach is used together with an optimization algorithm to minimize the discrepancy between the measured and predicted sound pressure spectra. This allows the frequency and angle dependent reflection and absorption coefficients of the material specimen to be calculated in an extended frequency range. The method has been tested successfully on samples of melamine foam and wood fiber. The measured data are in close agreement with the predictions by the equivalent fluid model for the acoustical properties of porous media.

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The combined length of the sewerage and clean water pipe infrastructure in the UK is estimated to be about 800,000 km. It is prone to failure due to its age and the inadequacies of the current pipe inspection methods. Fibre-optic cable sensing is an attractive way to continuously monitor this infrastructure to detect critical changes. This paper reviews the existing fibre-optic sensor (FOS) technologies to suggest that these technologies have better sensing potential than traditional inspection and performance monitoring methods. This review also discusses the requirements for retrofitting an existing pipeline with an FOS. It also demonstrates that there is a need for further research into methods applicable to non-pressurised pipelines, as there is very little existing literature that focuses on partially filled pipes and pipes with gravity fed flows.

This work presents a novel method of measurement of the absorption coefficient of large material samples in an acoustic waveguide in a broad frequency range. The material sample is deployed at one end of an acoustic waveguide the other end of which is excited with a point source. The sound pressure data are obtained using a long horizontal microphone array deployed in this waveguide. The optimization analysis is then applied to the sound pressure data to calculate the modal reflection coefficients, which are then combined to determine the overall absorption coefficient of the material sample placed at the end of this waveguide. It believed that this method will be able to extend significantly the frequency range attained with the current ISO 10543-2 impedance tube method and be applied to those materials which have a corrugated surface or complex surface morphology such as acoustic diffusers or living plants. It is also believed that this method will provide the means to estimate efficiently the diffusivity of materials with complex surface morphology with a relatively simple laboratory setup.

Sound intensity may be defined as a complex quantity in which the real part of the intensity is related to the magnitude of the local mean energy flow, and the imaginary part to the local oscillatory transport of energy. By treating intensity as a complex quantity it is possible to visualise energy flow in a different way and this has the potential to aid in the interpretation of, say, sound fields scattered by objects. Accordingly, the sound field scattered by an object placed in a semi-infinite circular duct is examined here. Experimental measurements of complex intensity are obtained in three (orthogonal) directions using a Microflown intensity probe, and measurements are compared to predictions obtained using a finite element based theoretical model. Comparisons between prediction and measurement are undertaken for both plane wave and multi-modal sound fields and here it is noted that when at least one higher order mode propagates it becomes more difficult to obtain good agreement between prediction and experiment for the complex intensity.

Over the recent years, it has become more and more apparent that creativityis a skill equally important for both technical and artistic careers. However,methods for teaching creativity that work for arts students are not alwaysappropriate for engineering students. The present study outlines theadaptation of a creativity development session from an artistic degreecurriculum (Mascarenas, 2019), to make it suitable for teaching toengineering students. The session was run three times with 1st and 2nd yearengineering students at a Russell Group university in the north of England,and both qualitative and quantitative feedback was collected from studentsafter the session. The main findings indicate the importance of a trustingrelationship between students and the educator, the need for balance betweendelivering a memorable experience and offering support, and the significanceof subsequent reflection.