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.
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.
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The City of Bellevue
The noise ordinance is located in Bellevue City Code Title 9.18, Noise Control. It restricts the noise level 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 to build a new single-family home or add 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.
City of Seattle
Seattle Municipal Code 25.08.410 regarding exterior sound level limits, states A. The exterior sound level limits are based on the Leq during the measurement interval using a minimum measurement interval of one minute for a constant sound source, or a one‐hour measurement for a non‐continuous sound source. For sound sources located within the City, the exterior sound level limits are as follows:
District of Sound Source
Residential Commercial Industrial
District of Receiving Property
Residential (dB(A)) (Leq)
55 57 60
Commercial (dB(A)) (Leq)
57 60 65
Industrial (dB(A)) (Leq)
60 65 70
Seattle Municipal Code 25.08.420 regarding night-time noise limits, states A. Between the hours of 10 p.m. and 7 a.m. during weekdays, and between the hours of 10 p.m. and 9 a.m. on weekends and legal holidays, the exterior sound level limits established by Section 25.08.410 are reduced by 10 dB(A) where the receiving property lies within a residential district of the City.
Contact us for a noise survey meeting City Code.
(1) In new construction, plans submitted under WAC 246-366-040 shall specify ventilation equipment and other mechanical noise sources in classrooms are designed to provide background sound which conforms to a noise criterion curve or equivalent not to exceed NC-35. The owner shall certify equipment and features are installed according to the approved plans.
(2) In new construction, the actual background noise at any student location within the classroom shall not exceed 45 dBA (Legx) and 70 dB (Leqx) (unweighted scale) where x is thirty seconds or more. The health officer shall determine compliance with this section when the ventilation system and the ventilation system's noise generating components, e.g., condenser, heat pump, etc., are in operation.
(3) Existing portable classrooms, constructed before January 1, 1990, moved from one site to another on the same school property or within the same school district are exempt from the requirements of this section if the portable classrooms meet the following:
(a) Noise abating or noise generating features shall not be altered in a manner that may increase noise levels;
(b) The portable classrooms were previously in use for general instruction;
(c) Ownership of the portable classrooms will remain the same; and
(d) The new site is in compliance with WAC 246-366-030(3).
(4) In new construction, the maximum ambient noise level in industrial arts, vocational agriculture and trade, and industrial classrooms shall not exceed 65 dBA when all fume and dust exhaust systems are operating.
(5) The maximum noise exposure for students in vocational education and music areas shall not exceed the levels specified in Table 1.
TABLE 1
MAXIMUM NOISE EXPOSURES PERMISSIBLE
|
Duration per day (hours) |
|
Sound Level (dBA) |
|||
|
8 |
|
hours |
|
85 |
|
|
6 |
|
hours |
|
87 |
|
|
4 |
|
hours |
|
90 |
|
|
3 |
|
hours |
|
92 |
|
|
2 |
|
hours |
|
95 |
|
|
1-1/2 |
|
hours |
|
97 |
|
|
1 |
|
hour |
|
100 |
|
|
1/2 |
|
hour |
|
105 |
|
|
1/4 |
|
hour |
|
110 |
|
Students shall not be exposed to sound levels equal to or greater than 115 dBA.
(6) Should the total noise exposure in vocational education and music areas exceed the levels specified in Table 1 of subsection (5) of this section, hearing protectors, e.g., ear plugs, muffs, etc., shall be provided to and used by the exposed students. Hearing protectors shall reduce student noise exposure to comply with the levels specified in Table 1 of subsection (5) of this section.
(1) No person shall cause or permit noise to intrude into the property of another person which noise exceeds the maximum permissible noise levels set forth below in this section.
(2)(a) The noise limitations established are as set forth in the following table after any applicable adjustments provided for herein are applied.
|
|
|||
|
|
Class A |
Class B |
Class C |
|
class a |
55 dBA |
57 dBA |
60 dBA |
|
class b |
57 |
60 |
65 |
|
class c |
60 |
65 |
70 |
(b) Between the hours of 10:00 p.m. and 7:00 a.m. the noise limitations of the foregoing table shall be reduced by 10 dBA for receiving property within Class A EDNAs.
(c) At any hour of the day or night the applicable noise limitations in (a) and (b) above may be exceeded for any receiving property by no more than:
(i) 5 dBA for a total of 15 minutes in any one-hour period; or
(ii) 10 dBA for a total of 5 minutes in any one-hour period; or
(iii) 15 dBA for a total of 1.5 minutes in any one-hour period.
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