You can use your cursor to view specific decibel levels and scroll back 24 hours, or click on the date display to view a different day. You can also click on the colored A, C, and Z “weighting” icons to see how they compare. For more information on weightings, see below.
The graph above shows sound-level data collected every minute by the Noise Project’s first sound monitor in Providence. The purple horizontal line is the city’s residential sound-level limit, which is 65 decibels (dB) from 7:00 a.m. to 10:00 p.m. and 55 dB from 10:00 p.m. to 7:00 a.m.
The monitor was deployed on the west side of the city on April 30, 2025 — the 30th annual International Noise Awareness Day. It designated as “DiRuzzo” in honor of former City Council member Josephine DiRuzzo, who advocated to reduce noise.1
It’s part of a planned city-wide network of sound monitors, designed to ascertain both baseline sound levels and daily / weekly / seasonal noise trends around Providence. The goal is to: 1) identify areas where residents face the most persistent exposure to unhealthy noise and when, and thus where the city should focus its abatement efforts, and 2) determine how effective those efforts actually are.
All green, orange, and blue lines above represent the exact same sound data, but two are “weighted” (i.e., filtered) to focus on certain frequency ranges. The green line is called “A-weighting,” which focuses on the mid-range frequencies corresponding to the human voice — by excluding most of the lower-range “bass” data.
By contrast, the orange line is “C-weighted” data, which retains much more of the low-frequency bass that comprises most of the excessive and unhealthy noise in Providence. The blue line is called “Z-weighted” data, but is actually unweighted — i.e., “raw” sound data with no weighting.
Like most U.S. municipalities, Providence uses A-weighted sound-measurement data that, as the graph above demonstrates, usually depicts decibel levels as being significantly lower than either C-weighted or unweighted data, and thus inaccurately represents actual noise levels in the city.
For that reason, the Noise Project supports the use of C-weighting rather than A-weighting. For more information on sound weighting — including a visual depiction of what the different weightings capture — and the exponential decibel scale, visit our “How Sound is Measured” page.
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1 See references to Ms. DiRuzzo’s advocacy on our PVD noise-policy timeline, beginning in 1995.