SDCI’s noise abatement group conducts inspections and noise advisory reviews for almost all residential side-yard mechanical installations. In a typical Neighborhood Residential zone, the Seattle Municipal Code (SMC) requires an overnight sound level limit of 45 dBA (decibels) at the property line during the overnight hours. Overnight hours are defined in SMC 25.08 as 10:00 p.m. to 7:00 a.m. weekdays and 10:00 p.m. to 9:00 a.m. weekends and legal holidays. Legal holidays are New Year’s Day, Memorial Day, Independence Day, Labor Day, Thanksgiving Day, Day after Thanksgiving, and Christmas Day. The 45 dBA standard is fairly restrictive because the City of Seattle makes resident’s ability to sleep and relax a major priority.
Since no one wants to be the person who keeps their neighborhood awake with low-frequency mechanical noise, planning out your mechanical project is key. When considering a new mechanical installation, it is important to have a conversation with your contractor about the noise impact from the equipment.
- Pre-installation review. Once you have an issued refrigeration permit for your project, the SDCI noise abatement group can review your proposed installation for compliance with SMC 25.08. The placement of your equipment is a critical decision, and if done incorrectly can cost more money and take time to resolve. An SDCI pre-installation review will identify any potential compliance issues, making you feel more confident about the project.
- Noise complaints. If SDCI receives a noise complaint regarding your mechanical installation, we will start our investigation by reviewing the property permit history. After that review, we contact the property owner and arrange a site inspection to take a compliance sound level. If the installation violates the SMC exterior sound limits, then we will give the property owner a timeline for a mitigation plan. SDCI will need to review the mitigation plan and, if accepted, will provide a timeline for compliance.
- Available resources. SDCI’s noise code webpage has several helpful resources, including Noise Tips for Siting Equipment, Sound Levels at Distances, Noise Barrier Example, Residential Heat Pump and A/C Installation Presentation, and more.