for variability in seasonal operations where certain times of the year may include
greater than normal frequency in operations. Noise sensitive uses are generally
acceptable within this area; however, this may vary on a case‐by‐case basis.
PK15(met). PK15(met) is the metric used to calculate a single‐event peak noise level
when factoring in unfavorable weather conditions that favors noise propagation. The
PK15(met) is expected to be exceeded only 15 percent of the time by the loudest
munitions type detonation. The PK15(met) metric does not communicate any
information about how often the loudest munitions type is detonated.
Sound attenuation. Sound attenuation is a reduction in the level of sound resulting from
an object’s distance from the noise source or absorption by the surrounding topography,
atmosphere, barriers, construction techniques and materials, and other factors. Sound
attenuation in buildings can be achieved through the use of special construction
practices, reducing the amount of noise that penetrates the windows, doors, and walls of
a building. Sound attenuation measures may be incorporated during initial construction
for new buildings or as additional construction for existing buildings.
Unweighted peak decibel (dBP). The unweighted peak decibel is the peak, single event
sound level on the ground, without any particular certainty–such as with the 85 percent
certainty built into the PK15(met) above. This is a real‐time measurement that is affected
by everything from the weather to the length of the grass. As such, it is highly variable.
Technical Background
Due to the technical nature of this compatibility factor and its importance to the JLUS
process, the following section provides a discussion of the characteristics of sound and
the modeling process used to evaluate noise impacts.
Characteristics of Sound
It is important to understand that there is no single perfect way of measuring sound, due
to variations used by different entities when conducting sound studies or sound
modeling. Sound is characterized by various parameters that include the oscillation rate
of sound waves (frequency), the speed of propagation, and the pressure level or energy
content (amplitude) of the waves. The sound pressure level has become the most
common descriptor used to characterize the loudness of an ambient sound level. The
decibel scale is used to quantify sound intensity. Because sound pressure can vary by
over one trillion times within the range of human hearing, a logarithmic loudness scale,
i.e., the dB scale, is used to present sound intensity levels in a convenient format.
The human ear is not equally sensitive to all frequencies within the entire spectrum, so
noise measurements are weighted more heavily within those frequencies of maximum
human sensitivity in a process called “A weighting,” written as dBA. The human ear can
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Compatibility Assessment