Noise zone. A noise zone is the area inside an identified noise contour.
Different noise zones are separated by their respective noise contours.
PK15(met). PK15(met) refers to the peak sound level that is likely to be
exceeded only 15% of the time at a given location, after factoring in the
statistical variations attributed to weather (i.e., 85% certainty that sound will be
within this range). PK15(met) exists only in modeling—one cannot take a
PK15(met) reading on the ground—and it is used for land use planning with
small arms and to supplement planning with large arms and other impulse
sounds.
Noise Zones
Day‐night average sound level (DNL) is used to represent an average sound exposure
over a 24‐hour period. During the nighttime period (10:00 p.m. to 7:00 a.m.), averages
are artificially increased by 10 dB. This weighting reflects the added intrusiveness and
the greater disturbance potential of nighttime noise events since community ambient
noise typically decreases by 10 dB at night. A weighted day‐night average sound level
(ADNL) is commonly used by the Federal Aviation Administration and the DoD to
represent aircraft noise levels, and C‐weighted day‐night average sound level (CDNL) is
commonly used by the DoD to describe large arms and demolitions noise levels.
PK15(met) decibels is the unit used to identify small arms weapons noise zones. The
AZARNG Statewide Operational Noise Management Plan, last updated in March 2011,
has modeled noise zones for AZARNG facilities in Arizona. Noise is categorized into four
different zones, which are described as follows and summarized in Table 3‐2.
Noise Zone III is the zone located closest to the source of noise. In this zone,
PK15(met) decibels are greater than 104 (for small arms), ADNL is greater than
75 (for aircraft), and/or CDNL is greater than 70 (for large arms and explosions).
No noise‐sensitive uses should occur within this area due to the severity of
noise.
Noise Zone II includes areas where the PK15(met) decibels are between 87 and
104, the ADNL is between 65 and 75, and/or the CDNL is between 62 and 70.
Although local conditions such as availability of developable land or cost may
require noise‐sensitive uses in Zone II, this type of land use is strongly
discouraged on the installation and in surrounding communities. All viable
alternatives should be considered to limit development in Zone II to
non‐noise‐sensitive uses such as industry, manufacturing, transportation,
agriculture, and open space / resource protection.
Noise Zone I does not have an established boundary and refers to land around a
noise source and outside of the Zone II contour where noise can be heard. In
this zone, PK15(met) decibels are less than 87 dB, the ADNL is less than 65, or
Background Report
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