The most common single number rating system for measuring the loudness of a noise. It maybe read directly on most sound level meters by selecting the designated scale. It is obtained by applying the A-weighted frequency response curve to the measured sound. The response curve is indicative of the way humans respond to different frequencies.
Process whereby a porous material extracts one or more substances from an atmosphere, a mixture of gases, or a mixture of liquids.
(1) Process in which fluid molecules are concentrated on a surface by chemical or physical forces or both; (2) surface adherence of a material in extracting one or more substances present in an atmosphere or mixture of gases and liquids, unaccompanied by physical or chemical change.
This is the line within the envelope of the dwelling where the barrier to air leakage will be. A system of materials that enclose a volume of air with minimal air leakage between the enclosed air and the exterior. The effectiveness or adequacy of the air barrier can be measured by the volume of air (in cubic feet per minute) that must be added or removed from the enclosure.
ACH is an acronym for Air Changes per Hour and is a measurement of air infiltration. It is the total volume of air in a home that is turned over in one hour.
Air control layers control airflow between a conditioned space and an unconditioned space or between units in multi-family and apartment construction. The air control layer system is the primary air enclosure boundary that separates indoor (conditioned) air and outdoor (unconditioned) air. In multi-unit/townhouse/apartment construction the air control layer system also separates the conditioned air from any given unit and adjacent units. Air control layer systems also typically define the location of the pressure boundary of the building enclosure. In multi-unit/townhouse/apartment construction the air control layer system is also the fire barrier and smoke barrier in inter-unit separations. In such assemblies the air control layer system must also meet the specific fire-resistance rating requirement for the given separation. Air control layer systems typically are assembled from materials (such as gypsum board, sealant, etc.) incorporated in assemblies (such as walls, roofs, etc.) that are interconnected to create enclosures.
The uncontrolled flow of air through gaps and cracks in the external envelope/fabric of buildings (sometimes referred to as air infiltration, exfiltration or draughts).
The physical property used to measure the airtightness of the building fabric. It is defined as air leakage per hour per square metre of envelope area (m3/h/m2) at a test reference pressure difference across the building envelope of 50 Pascals (Pa) or (50 N/m2).
Sound which arrives at the point of concern, such as one side of a wall, by propagation through air.
The degree of air leakage or air infiltration a building has. Making a building airtight essentially means eliminating draughts. Ideally we want to have total control over how much air we're letting in to the building through designed ventilation systems, rather than cold air entering (and warm air escaping) uncontrolled through unwanted or unseen gaps. Airtightness is typically measured in two units: air changes per hour at the pressure difference of 50 Pa (n50) and air permeability (m3/hr/m2). For a typical building, there is usually little difference in the two figures. The smaller the airtightness figure the better.
