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The following words, terms and phrases, when used in this article, shall have the meanings ascribed to them in this section, except where the context clearly indicates a different meaning:

A-weighted decibels, dB(A) means ten times the logarithm (to the base 10) of a power or intensity ratio with A-weighting which correlates with the human response to the loudness of sounds.

Composite transmission loss means the combined TL rating of all the exterior façade elements for a room or group of rooms, weighted based on the area and STC rating of each individual element.

Day-night sound level (LDN or DNL) means the yearly average of the A-weighted sound level integrated over a 24-hour period with a ten-decibel step function weighting on aircraft events between 10:00 p.m. and 6:59 a.m.

Facade elements means construction elements of the residence that comprise the building envelope from the outside surface of the element to the interior surface of the element. Typical façade elements are doors, windows, wall assemblies, roof assemblies, vents, fireplaces, etc.

Level reduction (LR) means, in a specified frequency band, the decrease in sound pressure level, measured at the location of the receiver when a barrier or other sound reducing element is placed between the source and the receiver.

Noise level reduction (NLR) means a reduction in A-weighted sound levels.

Outside to inside transmission loss (OITL), of a building facade, means in a specified frequency band ten times the common logarithm of the ratio of the airborne sound power incident on the exterior of the facade to the sound power transmitted by the facade and radiated to the interior. The quantity so obtained is expressed in decibels (dB).

Remodeling means any construction activity in a structure that includes but is not limited to:

(1) Any addition to the principle structure, or;

(2) Any interior or exterior alteration of an existing room that increases the square footage of that room.

Sound insulation means the capacity of a structure to prevent sound from reaching a receiving location.

Sound level, of airborne sound means a sound pressure level obtained using a signal to which a standard frequency weighting has been applied such as A-weighting.

Transmission loss (TL) of a partition means, for a specific frequency band, the difference between the average sound pressure levels in the source room and the receiving room (expressed in decibels) plus ten times the logarithm to the base 10 of the ratio of the area of the common partition to the total acoustical (sabine) absorption in the receiving room. Here partition may mean the façade element or combination of façade elements. The TL is determined either from ASTM E 90 (most current version) or ASTM E 966 (most current version). (Ord. No. 2011-07, § 2, 4-11-2011; Ord. No. 2006-78, § 1(Exh. A), 1-8-2007)

Cross reference: Definitions generally, § 1-2.