Noise source identification and noise reduction in a multi-state, centrifugal air compressor system

The objective of this research is to recommend practical noise control schemes for Hanwha Techwin’s multi-stage, centrifugal air compressors. For purpose of achieving this objective, far- and near-field noise measurements, sound intensity measurements, and structural vibration measurements were performed first to identify the acoustic characteristics of a compressor. Through these measurements, it was shown that the most dominant noise and vibration components were at the blade passing frequencies (BPFs) of the compression stage impellers. Thus, by suppressing these tonal BPF noise components, the overall noise level was reduced effectively. Here, Helmholtz resonators, dynamic dampers, noise insulation materials, and an enclosure were recommended to reduce these tonal noise components. The Helmholtz resonators could be used to reduce the overall SPL up to 3.5 dBA. By applying the mass dampers, 2.7 dBA reduction at 7 kHz and 1.5 dBA reduction at 10 kHz could be achieved. The installation of the sound insulation material could achieve 8 dBA overall SPL reduction. By installing the enclosure around the compressor, 4.3 dB reduction in the overall SPL could be achieved. To achieve a higher noise reduction using the enclosure, the size of leakage holes between the compressor pipe and the enclosure is recommended to be reduced.