TERMINOLOGY

Noise Criteria
Noise Criteria curves (NC) and Noise Rating (NR) have been developed to approximate loudness contours and speech interferance levels at particular frequencies. These criteria graphs indicate a soundpressure level at each frequency that will be appropriate in a particular environment. Sound levels are often expressed in A-weighted decibels (dba), having advantage of being easy to measure by sound level meter.

Sound Transmission Class
Sound Transmission Class (STC) values are used to describe airborne noise reduction characteristics in a single number form for building elements (materials) and construction. Transmission loss is measured in a laboratory according to ASTN standards E90. Data is collected in one-third octave bands (more precise than octave band data). Overall performance is described as STC, which is calculated using a weighted average of the one-third octave band TL data.

Thermal Conductivity
Thermal conductivity, or K-value (W/mK) is a measure of a materials ability to transfer heat through conduction and therefore is the principle property of an insulation material. The thermal conductivity of an insulating material will vary with the mean temperature under operating conditions. Typical thermal conductivity (K) values of insulation boards and blankets are derived from measurements taken in accordance with laboratory test methods. Materials with a high K value (conductor) include aluminium, concrete, and steel. Low K value (insulation) materials include fibreglass, polystyrene, and foam rubber. To save energy the heat transfer should be minimum.
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