Care must be taken to locate noise-producing mechanical equipment—such as heat pumps, air conditioners, and generators—so the noise produced during its operation is not excessive for neighboring properties. The city has maximum sound levels which must be met at each property line. These apply to equipment located on the roof, on the ground, outside the building, at an exterior wall, and inside a building where noise may be transmitted to an exterior wall through a duct and/or louver. Most noise problems occur between mid-evening and sunrise when ambient sound levels in the neighborhood are low due to less outdoor activity and traffic.
The City of Bellevue noise ordinance is located in Bellevue City Code Title 9.18, Noise Control. It restricts the level of noise at the property line in residential zoning districts to 45 dBA at night (10 p.m. to 7 a.m.) and 55 dBA during the day.
Land Use Code Section 20.20.525 requires an owner building a new single-family home or adding more than 1,000 square feet to an existing home to locate mechanical equipment in the rear yard, placed no less than five feet from any property line.
Other mechanical equipment (not a new home, not adding more than 1,000 square feet to an existing home) placed in the side yard outside of the minimum side-structure setback must include sound screening to reduce noise impacts.
The nighttime noise level of 45 dBA is similar to bird calls. Manufacturer specifications for mechanical equipment typically includes decibel ratings. For example, heat pumps and air conditioners are tested to a standard that gives them a manufacturer’s sound power rating usually in the 70–80 dBA range. This would require the mechanical equipment to be placed from 40 to 100 feet from the property line to meet maximum nighttime noise levels.
The most common method of reducing noise is to increase the distance between the noise- producing equipment and the property line. If obtaining the minimum distance is not an option, the owner may be required to get an acoustic report. The report may specify building a fence/insulated screen or enclosure, planting shrubs, limiting use to daytime only or moving the equipment.
The noise produced by rotating parts in units such as fans and motors can greatly increase if there is no preventive maintenance. Worn bearings and other limited-life parts, as well as loose screws, are a common source of buzzing and rattling noises.
We have a complaint-driven noise enforcement policy. Property owners are responsible for the noise their mechanical equipment produces, both at installation and during its operating life. At installation the mechanical inspector does not inspect for noise requirements. Should the city receive a complaint on the equipment, the property owner will be notified by our Code Compliance team, who may require an acoustic report verifying that the equipment in question complies with Bellevue codes.
Visit our mechanical permits page for more information.