Full scale model investigation on the acoustical protection of a balcony-like façade device (L).
The acoustical insertion losses produced by a balcony-like structure in front of a window are examined experimentally. The results suggest that the balcony ceiling is the most appropriate location for the installation of artificial sound absorption for the purpose of improving the broadband insertion loss, while the side walls are found to be the second best. Results also indicate that the acoustic modes of the balcony opening and the balcony cavity resonance in a direction normal to the window could have a great impact on the one-third octave band insertion losses. The maximum broadband road traffic noise insertion loss achieved is about 7 dB.
The sound transmission loss across ventilation window under active noise cancellation
An experimental investigation on the use of active noise cancellation to improve the sound transmission loss across a ventilation window was carried out in this study. This experiment series was conducted inside a building acoustic test chamber consisted of two isolated rooms. One of these rooms was reverberant and was used as the receiver room, while the other was made semi-anechoic and it was where the sound source was located. The ventilation window was installed on a brick wall separating these two rooms. Active control with one reference signal, one error microphone and maximum three secondary sources was implemented using the EZ-ANC II MIMO controller. Six well separated microphones which spanned over the whole volume of the receiver room were used to capture the average sound pressure level inside the receiver room. The average sound pressure levels in the receiver room with and without the active control were used to describe the improvement of sound transmission loss by the active control. Among the various control combinations tested, sound transmission loss improvement was found at frequencies below 550Hz. The highest improvement was ~5dB and was found at ~200 Hz. The improvement decreased as frequency increases in general, but there was a dip at ~300 Hz. This dip was believed to be due to a longitudinal resonance in the ventilation window cavity.
Tools for Sediment Management in Rivers
Sediment management, including supply and continual redistribution of sediments for channel maintenance and channel forming, is critical for effective environmental water programs. Many tools have been developed to more effectively manage sediment in rivers for ecosystem maintenance and improvement. This chapter reviews some of these tools, including sediment mobilization theory, environmental water requirements for geomorphic maintenance, and complementary options. Sediment mobilization theory addresses entrainment, transport, and deposition of sediment particles. Environmental flows assessment approaches that support geomorphic processes include threshold-based approaches, field/laboratory methods, and holistic methods. Complementary options for sediment management include catchment-scale conceptual models and budgets for sediment, basin land management (e.g., reforestation, better agriculture practices, etc.), sediment management through dams, and sediment augmentation below dams. These complementary options often have cobenefits with other management objectives. The chapter emphasizes that sediment management is generally complex, such that continual research is needed, ranging from improved sediment mobilization models to large-scale river experiments.