TP25-19 Sound Directivity Index and Influenece on Sound Power Calculation

CTI ATC-128 test code—2019 edition, carried forward to 2024 version—changed sound emission surfaces along with the associated sound power equation. Studies have examined the critical influence of Directivity Index (Di) and impact on sound power calculations. Correction factors may be necessary when testing for sound power of Heat Rejection Equipment (HRE) with negative Di values, where the primary sound contribution is from one or more sides as opposed to from above the unit. Through a comprehensive review of published sound data from various HRE configurations and further experimental testing, the research delves into the relationship between Di and the Sound Power Level (PWL) calculation methods of CTI ATC-128 and ISO-3744. A correction method is proposed to improve alignment between ATC-128 and ISO-3744 hemispherical results, aiding the project designer with consistency in environmental sound impact of a project. Girard, Kansas 66743