University of Pittsburgh Medical Center Cooling Tower
Introduction
UPMC Hospital in Pittsburgh, Pennsylvania has installed large cooling tower systems to provide chilled water for their extensive hospital facilities. However, residential areas are near the hospital, and the hospital received complaints about cooling tower noise shortly after installation of the additional cells. UPMC contacted David Coate Consulting (DCC) to assess the severity of the noise problem and to provide solutions.
Figure 1 shows measured cooling tower noise at a residence near the hospital. DCC conducted these measurements in order to determine the relative noise contributions between the existing Marley cooling towers and the new BAC towers. In addition, these measurements show the effect of fan speed on noise level and for comparison with ambient noise levels. These noise measurements show that the new BAC towers were the cause of the noise problem and 5 to 10 dBA attenuation would be required to restore the noise environment to its previous state.
DCC evaluated a number of mitigation options including low-noise fans, noise barriers, adding more cells (and reducing fan speed), intake and discharge attenuators, as well as building sound insulation treatments. The Marley towers had low-noise fans installed in 1991 which alleviated a similar noise situation. Figure 2 shows the Marley cooling towers.
Figure 2. Marley Cooling Tower
DCC found that the BAC fans produced noise levels proportional to 30logS (S=fan speed).
DCC recommended the installation of low noise fans as well as the construction of a noise barrier on top of the cooling tower. These measures reduced cooling tower noise to acceptable levels.