The last major revision of the current HUD noise regulation (Title 24 code of Federal Regulations Part 51 Subpart B) and assessment process occurred in 1979. In 2011, HUD sought to take into account changes in assessments, mitigation technology, and situations encountered in the field to inform the updating of these standards. David Coate was the principal researcher of this project, on behalf of ICF International. The following study areas were included in the acoustic research:
Transit Oriented Development
The growth in transit oriented development (TOD) initiatives in various cities throughout the U.S. is indicative of incentives realized from reduced automobile costs, lower emissions, availability of transit, convenience of being able to walk to nearby shops, and so on. Jurisdictions are also using TOD to bring about lasting revitalization in neighborhoods because families that use public transit spend less on transportation. HUD building projects can also coincide with TOD. However, since by definition buildings would be in close proximity to transit activities, it may not be obvious whether or not HUD’s noise requirements would be met.
A literature review was conducted to determine resources and techniques that could be used to supplement HUD noise guidance but yet determine whether or not the TOD project would be in compliance with HUD regulations.
Clarify Existing Building Policy
A literature review was conducted to clarify existing building policy. HUD and other relevant agency definitions that address existing vs. new structures, modernization/ rehabilitation, and reconstruction of structures (e.g., following a disaster) were reviewed. FEMA regulations and guidance, including cost-based thresholds were also reviewed.
The findings included (1) a definition of an existing building, “modernization” and “major or substantial rehabilitation” in quantifiable, project-based metrics, (2)identification of the type of assessment required for existing structures versus new construction, (3) recommendation for a mitigation requirement/strategy for existing buildings in high noise-exposed areas, and (4) guidance on replacement of existing structures in non-compliant locations with conditions or limits of replacement if justified.
Identify Standards to Control Noise from HUD Projects
Proposals are sometimes offered for HUD-assisted projects that would add sound sources, such as fire stations or truck traffic, to a neighborhood or a building. Both outdoor and indoor acoustic sources were could be an issue. Standards and codes that could be used to incorporate these types of uses into existing neighborhoods without deteriorating the existing sound environment were investigated.
Recommend Mitigation and Barrier Policy
HUD projects can require interior and/or exterior mitigation; however, HUD has had difficulty keeping up with the changes in building technology with regard to the sound attenuation characteristics of new materials and construction techniques. A number of noise mitigation metrics such as STC and metrics such as Outside/Inside Transmission Class were reviewed for possible application to HUD projects. Since noise barriers are often infeasible in urban environments, recent case studies to assess HUD barrier policy guidance were reviewed.
The study included (1) recommendations for a preferred mitigation measurement, (2) standards for sources and documentation for mitigation classifications, and (3) guidance for the acceptable type and placement of physical exterior barriers in urban landscapes.
Recommendations on Frequency and Impulse Sound
The current noise regulation does not consider the frequency of sound (as measured in Hertz) in its enforcement. The potential need for consideration of frequency in HUD regulations through a literature review in the acoustics scientific literature was considered. In addition, when the HUD standards were developed, there was a lack of consensus regarding impulsive sound (sudden loud sounds). Current impulsive sound standards were reviewed for possible inclusion in HUD guidance. A number of agency guidance and research, academic papers and journal articles, local noise ordinances, and industry publications were reviewed. Data sources included publications and papers from sources such as the Transportation Research Board ADC40 Noise Committee, Acoustical Society of America, Airport Noise Mitigation Symposium, Federal Interagency Committee on Aviation Noise, American Institute of Architects, and the Institute of Noise Control Engineering.
The study included (1) an annotated bibliography of research on the state of the science of acoustics as it relates to selected noise sources – wind turbines, helicopters, and transit systems in urban environments – and (2) recommendations for changes to the regulation that will allow the HUD to meet its policy goals in light of these issues.