Is fighting sound with sound the future for noise control? James Macneil hears how active noise technology is slowly being fine-tuned for commercial use.
To evaluate the health risk posed by particles emitted from sound absorbent materials used in ventilation channels, the number, size, shape and composition of fibers and other particles must be characterized. A method of studying those particle characteristics has been developed. The number concentration of small particles in the testing chamber was measured with a condensation nucleus counter. Both scanning electron microscopical and optical microscopical analyses were possible for filter samples because of the low particle concentration of background particles in the testing chamber.
The sound insulation provided by similar types of windows varies considerably. This paper describes experiments on a number of elements which affect sound insulation, including the sealing of openable panes, the type of frame material, the size of the window panes, and the spacing of panes in multiple pane systems. It identifies the main factors and lists the potential insulation values for various types of window. This paper will be of interest to architects, planners and acoustic consultants.
Building diagnosticians routinely use measurements of differential pressures, building and duct system airtightness, and mechanical system airflow when investigating air quality, comfort, durability, and energy use problems in commercial and residential buildings. Unfortunately, wind and other sources of noise can create large pressure fluctuations which significantly increase the variability of these measurements, often to the point where they can not be relied upon in the diagnosis of performance problems, or as quality control indicators.
This paper gives guidance on assessing the risk of surface condensation and mould growth at thermal bridges around openings in the external elements of buildings, and describes a method of assessing their effect on overall heat loss. It supports the 1995 revision of the Building Regulations for conservation of fuel and power.
Office noise affects the productivity of every person in every office. Companies have woken up to the detrimental effects on productivity of stale air pumped out by air-conditioning systems, and they are replacing these with natural ventilation systems. However, air-conditioning provides a useful by-product: the steady masking of background noise. Tom. Dawn considers the options for creating a better acoustical environment.
Radon is an inert radioactive gas released into the atmosphere from certain minerals and man-made products in which it is produced. It can accumulate in confined spaces. Radon emanation into a building can come from: the underlying soil, the building materials, tap water and natural gas. The principal isotope, 222Rn, decays to products which if inhaled can result in exposure of the respiratory tract to alpha radiation. The decay products, radon daughters, are significant because of their potential to cause health effects.
The acoustic environment was investigated in an office building with a history of occupant complaints. A scoring system was developed for rating occupants' sick building symptoms. High scores were associated with the occurrence of high levels of infrasound (< 20 Hz) in the rooms, und low levels with low scores. The infrasound came from the ventilation system as airborne noise, rather than structural-borne vibration. Levels of infrasound were often amplified in the tightly sealed rooms, and could be higher at work stations than at supply grilles.
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