A sound-measuring device rather an officer’s ears will judge whether Sandy Springs neighbors are too noisy in a new city code approved Feb. 20.

City officials feared the noise ordinance was too vague and unenforceable, so they moved to a decibel-based system with measurable limits on noise. That also means buying decibel meters that are “several hundred dollars apiece,” Assistant City Manager Jim Tolbert told the City Council.

The updated noise ordinance will go into effect July 1. That gives the city time to buy the meters, calibrate them and train staff members how to use them. Due to costs, only supervisors of the police and code enforcement departments will carry the devices, with regular officers use unscientific cellphone apps to get a rough idea of whether to call them in for the official measurement.

The main system set the noise limit as specific decibel levels for residential and commercial/mixed-use areas by day and night, or at 10 decibels above the ambient noise of the area, whichever is greater. However, there are several exceptions and special subsections of the noise law, and people can apply for variances.

Those main limits for residential areas are 65 decibels during the day and 55 decibels at night; for commercial/mixed-use, it’s 80 decibels during the day and 60 decibels at night. On public property like a sidewalk, the limit is 75 decibels.

The decibels are “A-weighted,” meaning they are measured in a way that is more sensitive to higher-frequency versions of noise, which are generally more annoying and harmful to the ear. The measurement is made from the property line or boundary; within a multifamily building unit, that’s at least 4 feet from the adjoining wall.

What do those decibel numbers mean in human terms? The code does not come with particular comparisons or descriptions. A chart made by the University of Maryland’s Trace Research & Development Center and posted online gives the following comparisons for A-weighted decibel levels:

55 decibels: Dishwasher running in an adjacent room

60 decibels: Normal conversation or office interior

70 decibels: Vacuum cleaner at 10 feet

80 decibels: Passing car at 10 feet or garbage disposal at 3 feet

During a City Council discussion about the ordinance change, Councilmember Steve Soteres said his noise-measuring cellphone app reported the council chamber was at 63.6 decibels during the conversation.

The decibel levels were decided by reviewing similar laws in several other cities.

The alternative measurement of 10 decibels over ambient noise was suggested by councilmembers, so that annoying behavior can be stopped even if it just as loud as everyday noise. Councilmember John Paulson noted that his neighborhood has background noise from Ga. 400 traffic that could be over the regular residential limit.

Among the exempted noise-making activities: Sanctioned activities at schools and parks, such as sporting events and marching bands; church bells; any type of First Amendment-protected gatherings of religious or political natures; public and private transportation vehicles; and trash collection. Playing a car stereo loud enough to be heard 100 feet away during the night, no matter the place or decibel level, is illegal.

The free speech protection may not extend to sidewalks under the code’s intent. The 75 decibel limit is aimed at such activities as street musicians, Tolbert said. “A lot of communities use this with street preachers,” he said.

The code sets separate decibel-level limits for non-commercial motor vehicles in two different speed limit zones, under and over 35 mph. Those limits: Vehicles over 6,000 pounds, 86/90 decibels; motorcycles, 82/86 decibels; other vehicles, 76/82 decibels.

Outdoor construction and landscaping are already restricted by day and hour, and those rules still apply. However, for noise purposes, such work will now be defined as 55 decibels or above.