[1] This work presents new water surface elevation data including evidence of the spatial correlation of water surface waves generated in shallow water flows over a gravel bed without appreciable bed forms. Careful laboratory experiments have shown that these water surface waves are not well-known gravity or capillary waves but are caused by a different physical phenomenon. In the flow conditions studied, the shear present in shallow flows generates flow structures, which rise and impact on the water-air interface. It is shown that the spatial correlation function observed for these water surface waves can be approximated by the following analytical expression W( ) = e -2 / 2 2 w cos(2 L -1 0 ). The proposed approximation depends on the spatial correlation radius, w , characteristic spatial period, L 0 , and spatial lag, . This approximation holds for all the hydraulic conditions examined in this study. It is shown that L 0 relates to the depth-averaged flow velocity and carries information on the shape of the vertical velocity profile and bed roughness. It is also shown that w is related to the hydraulic roughness and the flow Reynolds number.

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Acoustical sustainable materials, either natural or made from recycled materials, are quite often a valid alternative to traditional synthetic materials. The production of these materials generally has a lower environmental impact than conventional ones, though a proper analysis of their sustainability, through Life Cycle Assessment procedures, has to be carried out. Airborne sound insulation of natural materials such as flax or of recycled cellulose fibres is similar to the one of rock or glass wool. Many natural materials (bamboo, kenaf, coco fibres) show good sound absorbing performances; cork or recycled rubber layers can be very effective for impact sound insulation. These materials also show good thermal insulation properties, are often light and they are not harmful for human health. Furthermore, many of these materials are currently available on the market at competitive prices. There is however a need to complete their characterization, both from an experimental and a theoretical point of view, and especially to propose a standard and unique procedure to evaluate their sustainability. The paper presents an updated survey on the acoustical properties of sustainable materials, both natural and from recycled materials, including mixed and composite materials and systems such as green roofs and green walls, and is completed by a wide selection of recent related bibliography.

Frequency-wavenumber spectrum of the free surface of shallow turbulent flows over a rough boundary Data on the frequency-wavenumber spectra and dispersion relation of the dynamic water surface in an open channel flow are very scarce. In this work, new data on the frequency-wavenumber spectra were obtained in a rectangular laboratory flume with a rough bottom boundary, over a range of subcritical Froude numbers. These data were used to study the dispersion relation of the surface waves in such shallow turbulent water flows. The results show a complex pattern of surface waves, with a range of scales and velocities. When the mean surface velocity is faster than the minimum phase velocity of gravity-capillary waves, the wave pattern is dominated by stationary waves that interact with the static rough bed. There is a coherent three-dimensional pattern of radially propagating waves with the wavelength approximately equal to the wavelength of the stationary waves. Alongside these waves, there are freely propagating gravity-capillary waves that propagate mainly parallel to the mean flow, both upstream and downstream. In the flow conditions where the mean surface velocity is slower than the minimum phase velocity of gravitycapillary waves, patterns of non-dispersive waves are observed. It is suggested that these waves are forced by turbulence. The results demonstrate that the free surface carries information about the underlying turbulent flow. The knowledge obtained in this study paves the way for the development of novel airborne methods of non-invasive flow monitoring. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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The plane wave normal incidence acoustic absorption coefficient of five types of low growing plants is measured in the presence and absence of soil. These plants are generally used in green living walls and flower beds. Two types of soil are considered in this work: a light-density, man-made soil and a heavy-density natural clay base soil. The absorption coefficient data are obtained in the frequency range of 50-1600 Hz using a standard impedance tube of diameter 100 mm. The equivalent fluid model for sound propagation in rigid frame porous media proposed by Miki [J. Acoust. Soc. Jpn. (E) 11, 25-28 (1990)] is used to predict the experimentally observed behavior of the absorption coefficient spectra of soils, plants, and their combinations. Optimization analysis is employed to deduce the effective flow resistivity and tortuosity of plants which are assumed to behave acoustically as an equivalent fluid in a rigid frame porous medium. It is shown that the leaf area density and dominant angle of leaf orientation are two key morphological characteristics which can be used to predict accurately the effective flow resistivity and tortuosity of plants.

MEASUREMENT AND SUBJECTIVE ASSESSMENT OF WATER GENERATED SOUNDS ABSTRACTThere is increasing concern with protecting quiet and tranquil areas from intrusive noise. Noise reduction at source and barriers to transmission are mitigation measures often considered. An alternative is to attempt to mask or distract attention away from the noise source. The masking or distracting sound source should be pleasant so that it does not add to any irritation caused by the noise source alone. The laboratory measurements described in this paper consisted of capturing under controlled conditions the third octave band spectra of water falling onto water, gravel, bricks and small boulders and various combinations. These spectra were then matched with typical traffic noise spectra to assess the degree of masking that could be expected for each option. Recordings were also taken during each measurement and these were used later to enable the subjective assessment of the tranquillity of the sounds. It was found that there were differences between water sounds both in terms of masking and their subjective impact on tranquillity