[Code of Federal Regulations]
[Title 32, Volume 2]
[Revised as of July 1, 2008]
From the U.S. Government Printing Office via GPO Access
[CITE: 32CFR256.10]

[Page 601-602]
 
                       TITLE 32--NATIONAL DEFENSE
 
        CHAPTER I--OFFICE OF THE SECRETARY OF DEFENSE (CONTINUED)
 
PART 256_AIR INSTALLATIONS COMPATIBLE USE ZONES--Table of Contents
 
Sec. 256.10  Air installations compatible use zone noise descriptors.

    (a) Composite Noise Rating (CNR) and Noise Exposure Forecast (NEF) 
values as previously required by Sections III., IV., and V. of DoD 
Instruction 4165.57, ``Air Installations Compatible Use Zones,'' July 
30, 1973 \1\ will no longer be used.
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    \1\ Filed as part of original. Copies available in the Office of the 
Assistant Secretary of Defense (Installations and Logistics)--IO, 
Washington, DC 20301.
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    (b) Where CNR 100 (or the quietest boundary of CNR Zone 2 if 
otherwise computed) or NEF 30 would previously have been used, data 
shall be collected sufficient to permit computation of Ldn 65 noise 
contours and these noise contours shall be plotted on maps accompanying 
AICUZ studies.
    (c) Where CNR 115 (or the boundary of CNR Zone 3 if otherwise 
computed) or NEF 40 would previously have been used, data shall be 
collected sufficient to permit computation of Ldn 75 noise

[[Page 602]]

contours and these noise contours shall be plotted on maps accompanying 
AICUZ studies.
    (d) Where previous studies have used CNR or NEF, for meters of 
policy, noise planning and decisionmaking, areas quieter than Ldn 65 
shall be considered approximately equivalent to the previously used CNR 
Zone 1 and to areas quieter than NEF 30. The area between Ldn 65 and Ldn 
75 shall be considered approximately equivalent to the previously used 
CNR Zone 2 and to the area between NEF 30 and NEF 40. The area of higher 
noise than Ldn 75 shall be considered approximately equivalent to the 
previously used CNR Zone 3 and to noise higher the NEF 40. The 
procedures shall remain in effect only until sufficient data to compute 
land values can be obtained.
    (e) When computing helicopter noise levels using data collected from 
meters, a correction of +7db shall be added to meter readings obtained 
under conditions where blade slap was present until and unless matters 
are developed which more accurately reflect true conditions.
    (f) Noise contours less than Ldn 65 or more than Ldn 80 need not be 
plotted for AICUZ studies.
    (g) Since CNR noise levels are not normally directly convertible to 
Ldn values without introducing significant error, care should be 
exercised to assure that personnel do not revise previous studies by 
erroneously relabeling CNR contours to the approximately equivalent Ldn 
values.
    (h) Where intermittent impulse noises are such as are associated 
with bombing and gunnery ranges are of importance such noises will be 
measured using standard ``C'' weighing of the various frequencies to 
insure a description most representative of actual human response.