Mitigation Measures Below DNL 65dB

Presented To:	REDAC E&E Subcommittee

By:	Sean Doyle	AEE Noise Division (AEE-100)

Date: 	August 1, 2017

Federal Aviation

Administration

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Introduction

If policy updates result in lowered noise thresholds, then strategies for alternative mitigation options for noise levels below DNL 65dB may be a key consideration

As part of FAA’s larger policy review process, research efforts are now engaged in:

Supporting FAA review and consideration of Noise Policy updates that will accompany findings from community noise and annoyance survey

Evaluating efficacy of existing noise mitigation programs and potential for alternative noise mitigation options 

Providing concepts for mitigation at noise levels where existing mitigation techniques may not be as effective or appropriate 

Considering alternative mitigation options separate from standard physical treatments

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Federal Aviation

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Existing Sound Insulation Treatments

Current aircraft noise mitigation focuses on Sound Insulation Programs

For eligible residential homes*, funds are provided to replace exterior window and doors with those having better acoustic noise level reduction (NLR) properties.  HVAC systems may also be added as an incentive to reduce noise exposure by keeping doors and windows closed

Current eligibility requires that homes experience an exterior noise level of DNL 65dB or greater and that treatments would be needed in order to obtain a DNL 45dB interior noise level.  Treatments must also be shown to result in at least a 5dB decrease in interior noise level

*Mitigation programs may also include non-residential structures like Schools with additional approval and requirements

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Federal Aviation

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Mitigation Eligibility Beyond DNL 65dB

Most homes experiencing less than DNL 65dB exterior noise, will already achieve an interior Noise Level of DNL 45dB without added treatments

The DNL 45dB Interior criteria is supported as a “Natural Indoor Noise Floor” consistent with the ambient interior noise level of a typical indoor environment

A typical NLR level for an un-treated home already exceeds 20 dB

Sound Insulation treatments are therefore typically not required to achieve indoor noise levels below DNL 45 dB 

The need for and eligibility requirements for alternative treatments below DNL 65 dB will therefore require additional consideration

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Noise Level Reduction Distribution

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Potential Alternative Mitigation Options

If land use compatibility noise thresholds are lowered below DNL 65dB an expectation of additional mitigation at the new thresholds may result

To understand what type of possibilities may be of interest, two groups of stakeholders were polled

Sound Insulation Program Managers: Industry experts who complete evaluation and analysis of homes for sound insulation eligibility

Airport Operator Representatives: Airport Directors or Noise Office Directors who are aware of their communities’ perspective on noise exposure

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Federal Aviation

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Program Manager Feedback

Structural

HVAC Only

Mitigate Exposed Façade Only

Mitigate Eligible Rooms Only

Mitigate Homeowner Room of Preference

Secondary Treatment Package

Allow Homeowner to Upgrade Non-Treatable room to Habitable Indoor Space

Provide Acoustical Audit / DIY Guide

Provide Focused Treatments

Provide a Menu of Treatment Options

Compensatory

Monetary Compensation

Local Property Tax Breaks

Low Interest Bank Loans

Grants for Sound Insulation Improvements

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Other

Landscaping / Ground Cover

Active Noise Control

Masking Noise / Soundscape System

Exterior Roll-Down Shutters

Mass Loaded /Leaded Vinyl Curtains

Relocation / Sales Assistance

Passenger Facility Charge Use 

Mitigate NextGen Corridors  

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Airport Operator Feedback

Acoustical audit of homes along with some subsidized  mitigation or cost sharing between for home improvements

Installation of ventilation or central air conditioning (and not new doors/windows)

Input on Flight Procedure changes to reduce noise exposure

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Feasibility Estimates

From Program Manager and Airport Operator feedback, the suggested mitigation topics are being evaluated for feasibility

Priority is being given to the Airport Operator feedback, but where applicable, elements from the Program Manager feedback is also being reviewed

The feasibility review will include:

Economic estimates of application costs

Consideration of eligibility criteria

Identify areas needing additional consideration to determine how to implement alternative mitigation options

These finding will be used to support FAA deliberations on potential updates to current noise threshold and noise policy  

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Sean Doyle

Noise Division

Federal Aviation Administration Office of Environment and Energy

Email: sean.doyle@faa.gov

Federal Aviation

Administration

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