The FAA has issued an NPRM regarding noise standards on helicopters.  The full document is here, and we summarise it as follows

Summary

This rulemaking proposes to adopt more stringent noise certification standards for helicopters that are certificated in the United States (U.S.). This rule would apply to applications for a new helicopter type design and for a supplemental type certificate for those new type designs. A helicopter type certificated under this standard would be designated as a Stage 3 helicopter. This rule proposes to adopt the same noise certification standards for helicopters that exist in the standards of the International Civil Aviation Organization (ICAO). The proposal of these more stringent noise certification standards into U.S. regulations is consistent with the FAA’s goal of harmonizing U.S. regulations with international standards.

Background
ICAO Noise Certification Standards The International Civil Aviation Organization (ICAO) is the international body with the responsibility for the development of international standards under the Convention on International Civil Aviation (the Chicago Convention). Consistent with their obligations under the Chicago Convention, Contracting States agree to implement ICAO standards in their national regulations to the extent practicable. The United States is a Contracting State to the ICAO. The standards for aircraft noise are contained in ICAO Annex 16, Environmental Protection, Volume 1, Aircraft Noise.

In 1997, ICAO’s Committee on Aviation Environmental Protection (CAEP) chartered the Rotorcraft Task Group (RTG) to study potential increases in the stringency of noise certification standards for helicopters. The FAA participated in the RTG from 1997 to 2000. By the fifth session of CAEP in 2001, more stringent noise standards for helicopters were defined. These standards prescribe the lowering of noise limits for new helicopter types while using the same helicopter noise certification test procedures that the United States had incorporated into part 36, Appendices H (1988) and J (1992). On June 29, 2001, CAEP’s proposed noise stringency increases were adopted by the ICAO Council for incorporation into Annex 16, Volume 1, Chapter 8 and Chapter 11 (Amendment 7). ICAO guidelines became effective on October 29, 2001, with an applicability date of March 21, 2002.

Statement of the Problem Although ICAO adopted increased noise stringency standards for helicopters in 2002, the United States has yet to adopt these standards into part 36. There has been heightened public awareness of helicopter noise in the United States, and the FAA has determined that the public would benefit from adoption of these more stringent standards. The FAA’s adoption of these more stringent certification standards into part 36, including in Appendices H and J, would also satisfy the goal of harmonizing U.S. regulations with international standards. This rulemaking proposes to adopt the same noise certification standards for helicopters that exist in ICAO Annex 16, Volume 1, Chapter8 and Chapter 11 (Amendment 7).

General Discussion of the Proposal
This rulemaking proposes more stringent noise limits for helicopters to be type certificated in the United States. The standards would apply to the issuance of a new type certificate, and subsequent changes to a type certificate for which application is made after the effective date of this rule. This rule proposes to incorporate the same standards for helicopters adopted in ICAO Annex 16, Volume 1, Chapter 8 and Chapter 11 (Amendment 7), consistent with the FAA goal of harmonization of regulations with international standards.

These proposed regulations would:
• Amend § 36.1 noise certification standards for the issuance of type and airworthiness certificates for helicopters, including new definitions and an applicability date for the standards;
• Revise § 36.11 acoustical change requirements to include Stage 3 helicopters;
• Amend § 36.805 to add dates of applicability for the new Stage 3 noise limits prescribed in appendices H and J of part 36;
• Amend Appendix H to part 36 to include new noise certification limits for Stage 3 helicopters of all helicopter weights; and
• Amend Appendix J to part 36 to include a new noise certification limit for Stage 3 helicopters of 7,000 pounds or less.