Cellular telephone providers must submit applications for new cell tower installations to the City of Eugene's Planning and Development Department. The installations usually include cooling units and emergency generators. The applications must contain a noise component demonstrating prospective compliance with the city code. Engaged by the city, TNC serves to review these filings and critically evaluate the applicant's modeling inputs and assumptions, based upon data either provided by the applicant or independently researched. These reviews often extend over several rounds of request and response, resulting in a final report of findings to guide Planning staff.
In general, solar energy farms are particularly quiet; however, the power inverters needed to convert direct current (DC) into alternating current (AC) do emit a distinct tonal sound. The focus of the acoustical study was on the sound emission from the inverter units.
An acoustical analysis was performed to assess both acoustical impact and to determine regulatory compliance. This analysis included: assessment of the existing ambient sound levels; determination of source sound levels of power inverters (SatCon Power System - 500-KW and 1-MW units) and associated equipment at distances representative of the property line of adjacent residences and public rights-of-way; comparison of the modeled source sound levels at receptors to measured ambient sound levels and to permissible limits of the New Jersey Noise Code (NJAC 7:29); and, review of site plans and related documents including the Holland Township Code, Chapter 100, section 33, Noise.
The objective of the acoustical analysis was to determine the setback distance(s) of the inverter unit(s) from adjacent property lines to ensure compliance with the permissible limits of the New Jersey Noise Code at the residential property boundary and, more conservatively, to have no acoustical impact (i.e., source sound level at or below the ambient sound level) at or beyond the property line. Expert testimony was given before town planning board. It was demonstrated that the solar farm would be in compliance once operational and it received approval.