Strutt|Input Data|Empirical|Cooling Tower Half Speed Correction inserts the correction for half-speed operation of a cooling tower into the current row of the worksheet.
The correction is based on the ratio of the frequency band to the blade passage frequency of the cooling tower fan. In cases where the blade passage frequency is unknown, it is assumed to occur in the 63 Hz band for propeller-type cooling towers and 250 Hz band for centrifugal-type cooling towers.
Reference: Laymon Miller Noise Control for Buildings and Manufacturing Plants Section 7-11E