[Code of Federal Regulations]

[Title 24, Volume 1]

[Revised as of April 1, 2006]

From the U.S. Government Printing Office via GPO Access

[CITE: 24CFR51.103]



[Page 382-383]

 

                 TITLE 24--HOUSING AND URBAN DEVELOPMENT

 

PART 51_ENVIRONMENTAL CRITERIA AND STANDARDS--Table of Contents

 

                  Subpart B_Noise Abatement and Control

 

Sec.  51.103  Criteria and standards.



    These standards apply to all programs as indicated in Sec.  51.101.

    (a) Measure of external noise environments. The magnitude of the 

external noise environment at a site is determined by the value of the 

day-night average sound level produced as the result of the accumulation 

of noise from all sources contributing to the external noise environment 

at the site. Day-night average sound level, abbreviated as DNL and 

symbolized as Ldn, is the 24-hour average sound level, in 

decibels, obtained after addition of 10 decibels to sound levels in the 

night from 10 p.m. to 7 a.m. Mathematical expressions for average sound 

level and day-night average sound level are stated in the Appendix I to 

this subpart.

    (b) Loud impulsive sounds. On an interim basis, when loud impulsive 

sounds, such as explosions or sonic booms, are experienced at a site, 

the day-night average sound level produced by the loud impulsive sounds 

alone shall have 8 decibels added to it in assessing the acceptability 

of the site (see Appendix I to this subpart). Alternatively, the C-

weighted day-night average sound level (LCdn) may be used 

without the 8 decibel addition, as indicated in Sec.  51.106(a)(3). 

Methods for assessing the contribution of loud impulsive sounds to day-

night average sound level at a site and mathematical expressions for 

determining whether a sound is classed as ``loud impulsive'' are 

provided in the Appendix I to this subpart.

    (c) Exterior standards. (1) The degree of acceptability of the noise 

environment at a site is determined by the sound levels external to 

buildings or other facilities containing noise sensitive uses. The 

standards shall usually apply at a location 2 meters (6.5 feet) from the 

building housing noise sensitive activities in the direction of the 

predominant noise source. Where the building location is undetermined, 

the standards shall apply 2 meters (6.5 feet) from the building setback 

line nearest to the predominant noise source. The standards shall also 

apply at other locations where it is determined that quiet outdoor space 

is required in an area ancillary to the principal use on the site.

    (2) The noise environment inside a building is considered acceptable 

if: (i) The noise environment external to the building complies with 

these standards, and (ii) the building is constructed in a manner common 

to the area or, if of uncommon construction, has at least the equivalent 

noise attenuation characteristics.



                      Site Acceptability Standards

------------------------------------------------------------------------

                                   Day-night average         Special

                                    sound level (in       approvals and

                                       decibels)          requirements

------------------------------------------------------------------------

Acceptable....................  Not exceeding 65 dB(1)  None.

Normally Unacceptable.........  Above 65 dB but not     Special

                                 exceeding 75 dB.        Approvals (2)

                                                        Environmental

                                                         Review (3).



[[Page 383]]





                                                        Attenuation (4).

Unacceptable..................  Above 75 dB...........  Special

                                                         Approvals (2).

                                                        Environmental

                                                         Review (3).

                                                        Attenuation (5).

------------------------------------------------------------------------

Notes: (1) Acceptable threshold may be shifted to 70 dB in special

  circumstances pursuant to Sec.   51.105(a).

(2) See Sec.   51.104(b) for requirements.

(3) See Sec.   51.104(b) for requirements.

(4) 5 dB additional attenuation required for sites above 65 dB but not

  exceeding 70 dB and 10 dB additional attenuation required for sites

  above 70 dB but not exceeding 75 dB. (See Sec.   51.104(a).)

(5) Attenuation measures to be submitted to the Assistant Secretary for

  CPD for approval on a case-by-case basis.





[44 FR 40861, July 12, 1979, as amended at 49 FR 12214, Mar. 29, 1984]