Equipment sound data—What we want and how to get it

Data center construction and commissioning continues to grow at a fast pace. Noise control engineers and equipment vendors have an important role to play in ensuring that these facilities can function at the cutting edge, as good neighbors. Large mechanical equipment items like air-cooled chillers are the primary source of data center noise, and accurate knowledge of their noise emission characteristics is critical in the design of appropriate engineering controls. The total sound power level of large outdoor air-conditioning equipment can be quantified using the AHRI 370 standard, which provides methods to estimate sound power using pressure and intensity field measurements. While both field methods can estimate the total sound power level, the intensity method can also quantify the power on each radiating plane, for later computer modeling of source directivity. Additional useful information can be determined from intensity measurements using holography techniques that map the local intensity to a visual image. This paper will present a “wish list” for vendor equipment sound data to address questions of source directivity, low-frequency noise, and one-third octave-band assessment methods. We will share our recent experience conducting AHRI 370 measurements using pressure, intensity, and near-field acoustic holography methods.