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Acoustical Testing Results for SIRRPP — September 2025

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Port of Seattle
Noise Mitigation
SIRRPP HMMH Acoustic Testing

In August 2025, acoustical engineering firm HMMH measured indoor noise levels at 31 homes near Seattle-Tacoma International Airport to assess eligibility for the airport's Sound Insulation Repair and Replacement Program. Testing found that only one of the 31 homes met the FAA's minimum threshold of 45 decibels interior Day-Night Average Sound Level required to qualify for full sound insulation treatment, while seven additional homes had at least one room exceeding that level. The study used FAA-approved methods, including a Boeing 737-800 aircraft noise spectrum, to calculate how much airport noise penetrates each habitable room with windows closed.

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Notes

Technical memorandum from Harris Miller Miller & Hanson Inc. (HMMH), authored by Eric Cox, to Julie Kinzie at Sea-Tac Airport (SEA), reporting acoustical testing results for the SEA Repair and Replacement Program conducted in August 2025. Covers median interior Day-Night Average Sound Level (DNL) measurements for 31 residential structures in SeaTac, Burien, and Des Moines located within the 65–70 dB noise contour interval per the 2018 Forecast Condition Noise Exposure Map (NEM). Testing used HBK Model 2245 sound level meter, Mackie SRM450 loudspeaker (pink noise), and Boeing 737-800 representative aircraft spectrum per FAA AC 150/5000-9B Section 8.5.10.1. One structure meets the 45 dB median interior DNL threshold under FAA Order 5100.38D Appendix R; seven additional structures have individual rooms above 45 dB. Addresses on 13th Ave S and 14th Ave S in SeaTac and Des Moines, and 16th Ave S in Burien. HMMH Project Number 03-12150.001.004.

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