Introduction
In response to community concerns about live music sound at BLU on the Water (E. Greenwich, Rhode Island), David Coate Consulting (DCC) designed a high STC stage enclosure. This design acts as a 'waveguide' to direct live music sound away from the immediately adjacent community. This sound reduction strategy has had a favorable response. Figure 1 shows the results of the CADNA model and noise contours emanating in the opposite direction of the community.
DCC performed acoustical tests to determine the acoustical performance of the stage/semi enclosure after construction. The acoustical tests were performed on 5-12-22 and repeated the same tests used prior to construction of the enclosure. Both pink noise and music were used for the tests. Frequency data, as well as overall dBA and dBC measurements were collected. For the sake of brevity and simplicity, just the pink noise results are reported here since pink noise represents a true ‘apples to apples’ comparison of results. In addition, since the new enclosure interior is intentionally highly absorptive, the stage ‘source’ sound levels between the previous and current stage tests are different. Nevertheless, the current tests do allow for a determination of the improvement.
Table 1 shows a summary of the overall test results:
Based on the data in Table 1, the overall enclosure Noise Level Reduction at the property line is 4.7 dBA which is lower than predicted/designed. Subjective listening tests indicate that an unexpected amount of high frequency sound (e.g., clearly understanding words in the music) is likely due to reflected sound energy off of various surfaces (walls, deck, tent structure, etc.). Nevertheless, the overall improvement at the property line is 11.8 dBA which constitutes more than a 50% reduction in perceived loudness compared to existing conditions. This improvement assumes that 90.5 dBA can be maintained at the stage.
The pink noise level of 43.8 dBA at 88 King Street is very low, and at about measured ambient sound levels during tests.
The 52.8 dBA property line value corresponds to 61.8 dBC. Both of these values are well below the Town’s noise ordinance of 60 dBA and 65 dBC. However, it is important to restate from our previous reports that 65 dBC is an unrealistic limit for this situation which is evidenced by the fact that non music ambient sound sources routinely exceed 65 dBC by a wide margin.