A centrifugal compressor for fuel-cell vehicles, which makes compressed air and sends it to the fuel-cell stack, is investigated in this paper. It is the only part of revolution in the system, and it consumes most of the system power. Therefore, it is important to achieve low noise level as well as high efficiency. The operating line of this compressor is determined along the highest efficiency points and during the design-point operation the blade tone noise is the main contributor. It is widely known that the blade passing frequency (BPF) noise components is due to the circumferential flow fluctuations of the impeller. So the noise spectrum of this compressor needs to be examined closely. So, an experimental study is designed to investigate the aero-acoustic characteristics of a centrifugal compressor in detail. The existing system is modified to allow pressure measurements at the inlet and outlet of the impeller. Four microphone probes are also installed to determine the noise level in an isolated room. Tests are carried out to investigate the phenomena governing the tonal noise and the dominant noise source of the centrifugal compressor. With such information on noise, a design optimization process is carried out to determine a superior design point which will guarantee good performance and low noise level at the design point. The optimization is performed using the surrogate management framework with the simulated results obtained at sampled points. The final optimal design point and the comparison between the optimal designed compressor and the existing centrifugal compressor are described in the last section of this paper.

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