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 minute-by-minute sound-level data collected by the Noise Project’s very first noise monitor in Providence, which was deployed on April 30, 2025 — the 30th annual International Noise Awareness Day. It is located on the west side of the city and designated as “DiRuzzo” in honor of former City Council member Josephine DiRuzzo, who advocated to reduce noise.1
It was the first in 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 thus where the city should focus its abatement efforts, and 2) determine how effective those efforts actually are.
All three colored data lines above represent the same sound data, but two are “weighted” (filtered) to (de-)emphasize certain frequency ranges. The green line is called “A-weighting,” which emphasizes frequencies that correspond to the human voice, by filtering out most lower-range “bass” ones.
The orange line is “C-weighted” data, which retains much more of the low-frequency bass that comprises most 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). You can click on the colored icons in the graph to compare how different weightings display the same noise levels.
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 Footnote pending