A comprehensive guideline established by the U.S. Department of Housing.
One of the most comprehensive guidelines established can be obtained from the U.S. Department of Housing and Urban Development in the Guide to Airborne, Impact, and Structure Borne Noise Control in Multifamily Dwellings.
Descriptive definitions of three grades of acoustic environments are given in order to ascribe criteria suitable to the wide range of urban developments, geographic locations, economic conditions and other factors involved in the areas of concern of the FHA. Constructions meeting the criteria will provide good sound insulation and satisfy most of the occupants in buildings fitting the conditions of each grade.
Grade I: Luxury rating
Grade I is applicable primarily in suburban and peripheral suburban residential areas, which might be considered as the “quiet” locations and as such the nighttime exterior noise levels might be about 35-40 dB(A) or lower, as measured using the “A” weighting network of sound level meter which meets the current standards. The recommended permissible interior noise environment is characterized by noise criteria of NC 20-25 (32 dB(A)). In addition, the insulation criteria of this grade are applicable in certain special cases such as dwelling units above the eighth floor in highrise buildings and the better class or “luxury” buildings, regardless of location.
Grade II: Average Rating
Grade II is the most important category and is applicable primarily in residential urban and suburban areas considered to have the “average” noise environment. The nighttime exterior noise levels might be about 40-45 dB(A); and the permissible interior noise environment should not exceed NC 25-30 (37dB(A)) characteristics.
Grade III: Minimum Rating
Grade III criteria should be considered as minimal recommendations and are applicable in some urban areas which generally are considered as “noisy” locations. The nighttime exterior noise levels might be about 55 dB(A) or higher. It is recommended that the interior noise environment should not exceed the NC 35 (42 dB(A)) characteristic.
The most desirable plan would have the floor-ceiling assembly separating spaces with equivalent functions, e.g. living room above living room, etc.; however when this arrangement is not feasible the assembly must have greater acoustical insulating properties.
This arrangement requires greater impact sound insulation than the converse, where a sensitive area is above a less sensitive area. Or dining, or family, or recreation room.
The airborne STC criteria in this table apply as well to vertical partitions between these two spaces.
This arrangement requires equivalent airborne sound insulation and perhaps less impact sound insulation than the converse.