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Acoustical Testing Results for SIRRPP — May 2026

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Port of Seattle
Noise Mitigation
SIRRPP HMMH Acoustic Testing

Harris Miller Miller & Hanson Inc. (HMMH) conducted sound insulation testing at 30 homes near Seattle-Tacoma International Airport (SEA) in March 2026 to measure how much aircraft noise penetrates indoors. The study found that none of the 30 homes exceeded the FAA's 45-decibel interior noise threshold required to qualify for sound insulation treatments under current federal policy. However, nine homes had at least one individual room where interior noise levels surpassed 45 decibels, suggesting those specific rooms could benefit from upgraded windows or doors.

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Notes

Technical memorandum from Harris Miller Miller & Hanson (HMMH) to Julie Kinzie, Sr. Environmental Program Manager Sound Insulation, reporting acoustical testing results for the Seattle-Tacoma International Airport (SEA) Repair and Replacement Program, March 2026. HMMH measured median interior Day-Night Average Sound Level (DNL) for 30 residential structures in Des Moines, Burien, and Seattle using HBK Model 2245 sound level meter and Mackie SRM450 loudspeaker pink noise source, per FAA Advisory Circular 150/5000-9B Chapter 8 and FAA Order 5100.38D Appendix R. Results show no structures exceed the 45 dB median interior DNL qualification threshold; however, nine structures have individual habitable rooms above 45 dB DNL, including addresses on 9th Ave S, 10th Ave S, 13th Ave S, 14th Ave S, and 16th Ave S. Noise Level Reduction (NLR) was calculated using Boeing 737-800 representative aircraft spectrum per Section 8.5.10.1. Exterior DNL assigned as 70 dB per 2018 Forecast Condition Noise Exposure Map (NEM). HMMH Project Number 03-12150.001.004.

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