Mitigation assessment of complex noise sources - an acoustical camera approach

A complex noise source is a set of multiple noise sources operating in proximity. Segregation of individual sub-sources based on sound characteristics and loudness is often the goal but can be challenging. This case study presents one such complex noise source, a high-speed offset printer in a large-scale printing facility. This printer is an assembly of several modules spanning approximately 40 feet in length. The sound field in the printer area was complex because of many mechanical components propagating sound through air (air-borne), through equipment casing (structure-borne), and acoustical reflections from nearby surfaces. Localization of dominant sources is required to adequately design mitigation. To identify sub-sources a sophisticated acoustical camera was used for this study. An acoustical camera (SoundCam) is an advanced acoustical measurement device with an array of 64 microphones and an optical camera. The acoustic signals from the microphones are processed and visualized as sound levels contours in real-time as an optical image or video. Visualization of printer sound levels helped to identify dominant sub-sources and areas of sound reflection. Once the dominant sub-sources were identified, the sound levels were measured. This helped in developing targeted noise controls in comparatively short duration for a complex noise source.