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Acoustical Testing Results for SIRRPP — July 2025

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Port of Seattle
Noise Mitigation
SIRRPP HMMH Acoustic Testing

Harris Miller Miller & Hanson Inc. (HMMH) conducted sound insulation measurements at 30 homes near Seattle-Tacoma International Airport in June 2025 to determine whether interior noise levels meet the federal threshold for sound insulation assistance. Using FAA-approved testing methods, the study found that only 3 of the 30 homes had median interior Day-Night Average Sound Levels (DNL) at or above the qualifying 45 dB threshold, while an additional 3 homes had individual rooms exceeding that level. The results inform eligibility decisions under the SEA Repair and Replacement Program, which is governed by FAA Advisory Circular 150/5000-9B and the Airport Improvement Program Handbook.

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Notes

Technical memorandum from Harris Miller Miller & Hanson Inc. (HMMH), authored by Eric Cox and addressed to Julie Kinzie, reporting acoustical testing results for the Seattle-Tacoma International Airport (SEA) Repair and Replacement Program conducted in June 2025. HMMH measured median interior Day-Night Average Sound Level (DNL) values for 30 residential structures in SeaTac and Des Moines, WA, using HBK Model 2245 sound level meter and Mackie SRM450 loudspeaker pink noise source, per FAA AC 150/5000-9B Chapter 8 and Appendix R of FAA Order 5100.38D (AIP Handbook). Results show three structures qualify with median interior DNL ≥ 45 dB (eligibility threshold); three additional structures have individual rooms above 45 dB. Noise Level Reduction (NLR) calculated using Boeing 737-800 representative aircraft spectrum. Addresses tested include 12th Pl S, 13th Ave S, 14th Ave S, and 15th Ave S in SeaTac and Des Moines. HMMH Project Number 03-12150.001.004.

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