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Where shell and core work is included in the project scope, the following requirements shall be met. This requirement shall not be applied to tenant improvement-only projects.
  1. Exterior noise exposure for the project site shall be classified according to the categories shown in Table 1.2-3 (Categorization of Outpatient Facility Sites by Exterior Ambient Sound).
  2. The exterior noise classification category(ies) identified for a project site shall be used to determine the degree of sound attenuation required in the building façade due to sources of exterior noise, including sources being added by the facility.
  3. The building façade shall have a sound isolation rating (which depends on the site noise classification category) that complies with minimum exterior shell composite sound transmission ratings, either OITCc or STCc, as shown in Table 1.2-3 (Categorization of Outpatient Facility Sites by Exterior Ambient Sound).
A1.2-6.1.2.3 Exterior noise classifications. By means of exterior site observations or a sound-level monitoring survey and knowledge of new noise sources to be included in the design of the facility, the facility site should be classified into one of the noise exposure categories in Table 1.2-3 (Categorization of Outpatient Facility Site by Exterior Ambient Sound...). Further information for classifying sites according to exterior noise can be found in appendix table A1.2-b (Approximate Distance of Noise Sources for Use in Categorization of Outpatient Facility Sites by Exterior Ambient Sound).
  1. The sound levels for noise exposure categories A through D provided in Table 1.2-3 and appendix table A1.2-b should be used to evaluate required health care building envelope sound isolation and may differ from other such categorizations of community noise made elsewhere in this document.
    Category A-Minimal environmental sound. As typified by a rural or quiet suburban neighborhood with ambient sound suitable for single-family residences sound produced by transportation (highways, aircraft, and trains) or industrial activity may occasionally be audible but is only a minor feature of the acoustic environment.
    Category B-Moderate environmental sound. As typified by a busy suburban neighborhood with ambient sound suitable for multifamily residences sound produced by transportation or industrial activity is clearly audible and may at times dominate the environment but is not loud enough to interfere with normal conversation outdoors.
    Category C-Significant environmental sound. As typified by a commercial urban location, possibly with some large apartment buildings sound produced by transportation or industrial activity dominates the environment and often interferes with normal conversation outdoors.
    Category D-Extreme environmental sound. As typified by a commercial urban location immediately adjacent to transportation or industrial activities, sound nearly always interferes with normal conversation outdoors.
  2. Environmental noise on Category B, C, and D sites generally may be evaluated using the methods given for documenting site ambient sound levels using continuous sound monitoring over a minimum one-week period in ANSI/ASA S12.9: Quantities and Procedures for Description and Measurement of Environmental Sound, Part 2: "Measurement of Long-Term, Wide-Area Sound." This information should be used to determine detailed environmental noise control requirements for building design. Sites where ambient sound is influenced by airport operations may require additional monitoring as suggested in the ANSI standard to account for weather-related variations in aircraft sound exposure on site. In lieu of performing such additional monitoring, aircraft sound level contours available from the airport (if available) should be used to determine the day-night average sound level on-site produced by nearby aircraft operations. Sound-level monitoring on-site will still be needed to determine sound levels produced by other sources.
  3. Table 1.2-3 and appendix table A1.2-b present general descriptions for exterior sound exposure categories A through D, including distance from major transportation noise sources, ambient sound levels produced by other sound sources, and corresponding design goals for the sound isolation performance of the exterior building shell.
    The outdoor sound levels, expressed as A-weighted day-night average sound levels, are provided in the context of exterior building shell design. Outdoor patient areas may require lower sound levels, typically not exceeding a day-night average level of 50 dB. To achieve this may require accommodations such as exterior noise barriers or location of outdoor patient areas where the building structures provide shielding from noise sources.
  4. In most cases, following the requirements in Table 1.2-3 will result in interior day-night average sound levels (Ldn) from exterior sources that are less than or equal to 45 dBA. Actual results will vary depending on how well the sound-blocking ability of the shell at various frequencies matches the sound spectrum of the outdoor sound and other factors, such as the area of the exposed façade and sound absorption in the room.
    Some rooms require lower sound levels, such as assembly spaces, clinical spaces, quiet rooms, and similar noise-sensitive rooms. These room types should be carefully evaluated to reduce the contribution of outdoor noises transmitted inside while considering the noise levels from the building systems (see Table 1.2-5: Maximum Design Criteria for Noise in Interior Spaces Caused by Building Systems). Assemblies meeting the minimum OITCc requirement will typically provide better performance when the outdoor sound is dominated by sources with strong low-frequency sound (e.g., locomotives or slow-moving heavy trucks). Assemblies meeting the minimum STCc requirement typically provide better performance when strong low-frequency sound is not present.
    More detailed evaluation should be considered to identify which sound isolation rating (OITCc or STCc) is preferred to meet the exterior shell acoustic requirements and potentially provide a more cost-effective design.

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