As part of the planning for an offshore wind farm in Rhode Island coastal waters, an assessment of the potential acoustic effects on the ecosystem is being conducted. The developer has proposed to initially deploy eight 3.6‐MW wind turbines within 3 nm of Block Island. Two passive aquatic listener (PAL) systems were deployed south of Block Island from October 6 to November 11, 2008. Using data from the PALs, ambient noise histograms were computed for this pre‐construction phase. The largest sources of noise in the area at low frequencies were found to be from shipping, wind, rain, and biological sources. In addition, transmission loss measurements were also made in the region to calibrate a geoacoustic model. Measurements of airborne noise from a 1.5‐MW land‐based wind turbine already in operation in Rhode Island were made in 1/3‐octave bands and near the proposed windfarm site. A preliminary assessment of the effects of the offshore wind farm on marine animals at these sites will be presented. A plan for monitoring the noise field and potential biological effects during construction and operation of the windfarm is presented.