<div class="chunk-title">Sec. 8-39. - Definitions.</div>
<div class="chunk-content">
            <p class="p0">
               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:
               </p>
            <p class="p0">
               <span class="ital">A-weighted sound level (dBA)</span> means a number in decibels, which is read from a sound-level meter, when the meter
               is switched to its weighting scale labeled "A." The number approximately measures
               the relative noisiness or annoyance level of many common sounds, including aircraft.
               </p>
            <p class="p0">
               <span class="ital">Day-night average sound level (Ldn)</span> means a measure of noise which considers the 24-hour average sound level, 365 days
               a year, in A-weighted decibels. Those events occurring between 10:00 p.m. and 7:00
               a.m., incur a ten decibel penalty. This is the accepted parameter for determining
               the impacts of noise on people.
               </p>
            <p class="p0">
               <span class="ital">Decibel (dB)</span> means sound is measured in decibels. The zero on the decibel scale is based on the
               lowest sound level that the healthy, unimpaired human ear can detect. Decibels are
               not linear units, but representative points on a sharply rising (exponential) curve;
               i.e., an increase of ten decibels represent an approximate doubling of acoustic energy.
               </p>
            <p class="p0">
               <span class="ital">Effective perceived noise level (EPNL)</span> means a physical measure designed to estimate the effective noisiness of a single
               noise event, usually an aircraft flyover; it is derived from instantaneous perceived
               noise level (PNL) values by applying corrections for pure tones and for the duration
               of the noise.
               </p>
            <p class="p0">
               <span class="ital">Noise abative construction</span> includes insulation, storm windows and/or air conditioning designed to reduce interior
               noise due to aircraft activity. Landscaping may reduce ground noise, but has little
               impact on noise reduction from airborne produced noise.
               </p>
            <p class="p0">
               <span class="ital">Noise exposure forecast (NEF)</span> means a scale which has been used by the federal government in land use planning
               guides applied in connection with airports. In the NEF scale, the basic measure of
               magnitude for individual noise events is the effective perceived noise level (EPNL),
               in units of effective perceived noise decibels (EPNdb). This magnitude measure includes
               the effect of duration per event. The terms account for number of flights and for
               weighting by time period.
               </p>
            <p class="p0">
               <span class="ital">Sound transmission class (STC)</span> means a single-number rating which provides an estimate of sound transmissions loss
               performance of a wall or floor as related to airborne sound generated by a limited
               class of household sound sources. The higher the number, the better the performance.
               </p>
            <p class="p0">
               <span class="ital">Zone</span> means an area abutting and completely surrounding any airport in the county in which
               aircraft noise may occasionally interfere with certain activities of the residents.
               The zones are identified as land use guidance or "LUG" zones; "A," "B," "C," or "D."
               The zones are defined as:
               
               <p class="p1">
                  <span class="ital">Zone "A"</span> means that area having a day-night sound level (Ldn) of 55 and less.
                  </p>
               
               <p class="p1">
                  <span class="ital">Zone "B"</span> means that area having a day-night sound level (Ldn) between 55 and 65.
                  </p>
               
               <p class="p1">
                  <span class="ital">Zone "C"</span> means that area having a day-night sound level (Ldn) between 65 and 75.
                  </p>
               
               <p class="p1">
                  <span class="ital">Zone "D"</span> means that area having a day-night sound level (Ldn) of 75 or greater.
                  </p>
               
            <p class="historynote0">
               (Ord. of 5-21-2001, art. II, Â§ 2)
               </p></div>