Noise Level Reduction Measurement Method Equalization and Normalization
In 2014, the Federal Aviation Administration (FAA) amended the Airport Improvement Program (AIP) Handbook to clarify guidance for the funding of noise mitigation projects. Eligible structures are required to not only be located within the day-night average sound level (DNL) 65-decibel (dB) noise contour, but also experience existing interior noise levels that are 45 dB or greater with the windows closed. This restated guidance places greater emphasis on the measurement accuracy of the existing noise reduction of a structure.
The American Society for Testing and Materials (ASTM) E966-10Ɛ1 test procedure incorporates an outdoor loudspeaker to simulate an aircraft noise source. Adapting this procedure with outdoor and indoor noise level measurements is the most common approach for testing structures for noise level reduction. In 2017 and 2018, researchers investigated ASTM E966-10Ɛ1 adjustment factors and published DOT/FAA/TC-18-15, “Investigation of ASTM E966 Adjustment Factors,” which was the first phase of a guidance document for sound insulation measurement in airport sound insulation programs. This current study is the second phase, which was designed to specify the guidance requirements and identify areas where additional details to define a test procedure require validation by modeling and/or measurement.
Described in this report are (1) detailed analyses of the parameters that influence noise reduction measurements and (2) a measurement procedure outline for the noise level reduction of façades as part of an airport sound insulation program. This outline forms the basis for the development of a Society of Automotive Engineers International Recommended Practice for “Aircraft Noise Level Reduction Measurement of Building Façades.”
DOT/FAA/TC-19/34
Authors: Sharp, Ben H.; Cox, J. Eric; Zheng, Z.C.