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Noise Baseline Study
*see Ambient Noise Level Monitoring below
07/25/02
Start-up was slowed by equipment and software difficulties and unexpected construction at selected sampling sites. The challenges were overcome and monitoring is now being conducted on a quarterly basis at eight locations. Altered air traffic patterns following 9/11, since returned to normal, artificially raised levels at some locations. Nevertheless, when periodic or seasonal anomalies are identified and levels at all stations begin to stabilize, perhaps after 12 to 16 quarters, we will have sufficient data to begin developing noise contours. Using the GIS system, these contours can be mapped and continuously updated – a useful tool for transportation and land use planning and measuring program performance. As opportunity and resources allow, we will continue to add sampling stations to enhance coverage. A long-term goal (e.g., 10 years) is to increase the sampling frequency to bi-monthly, or even monthly, and eventually automate the system.
For maximum use of limited resources, the self-contained, portable all-weather noise monitoring system was built around our existing B&K Model 2236 Precision Sound Level Meter and the “Noise Explorer” software. The system, powered by a motorcycle battery, includes the instrument, an all weather case, a microphone extension cable and a tripod. Signs were fabricated indicating “Environmental Monitoring – Please Stay Clear”. All of the monitoring stations are owned either by the WSSC or municipalities. Results are reported as a 24-hour Leq, d BA (equivalent sound level as A-weighted decibels), further defined by the percentage metrics of L10, dBA and L90, dBA (that level exceeded 10% and 90%, respectively, of the time measured), to quantify the upper and lower ranges. We are also able to graphically present this data on an hourly basis. A long-term goal is to replace upgrade the sampling train to include telemetry and something equivalent to DAT recording technology to record anomalies when a predetermined trigger level is reached.
Ambient Noise Level Monitoring
Excessive noise from transportation, human activity, amplification and mechanical equipment interferes with the quiet enjoyment of property and the lawful conduct of business, generally diminishing the "quality of life" in the community. It raises the stress level of individuals and communities. Continued growth and urbanization, particularly in mixed-use zones, often creates an inherent conflict of equities.
The County Noise Ordinance sets single numerical daytime and nighttime receiving property line limits for noise, although the single standards ensure ease of implementation, they may not be entirely appropriate to adequately protect the quality of life in all communities.
In Fiscal Year 2001, the County will begin implementation of a continuous ambient monitoring program which will provide an assessment of the effectiveness of the Noise Ordinance. This program will also establish a baseline for subsequent comparison and identify specific noise sources which can then be targeted for specific abatement measures. If these sources are beyond County control (e.g., motor vehicles, highways, and aircraft), the verifiable data developed by the program demonstrating elevated noise levels will assist the County in lobbying for changes with the State and Federal governments.
Complaint Category Tracking & Analysis
Community noise prevention and control is a "quality of life" issue. Within certain technical and legal limitations, it is also what the community wants it to be. Noise problems, as with many quality of life issues, have a tendency to become aggravated if not addressed. This is especially important to the Police Department, which responds to the majority of off-hour complaints. Implementing noise control criteria provides a mechanism for working with communities to address their concerns in an effective and efficient manner.
While the County currently maintains a noise complaint tracking system, there are limitations inherent in its broad complaint categories. To more precisely pinpoint the nature of a specific complaint, thereby providing an accurate determination of community needs and concerns, and allowing for a proactive and preventative response, a comprehensive set of noise categories must be developed using available data and interviews with compliance personnel in concert with the Police Department. This new reporting system will permit the quarterly tabulation and analysis of complaints and will assist in providing category trend analysis, determining and measuring the effectiveness of specific reduction strategies, and help with the subsequent targeting of resources for prevention efforts.