A multi-channel real-time sound pressure spectrum analyzer was demonstrated for investigating abnormal noises of tapered roller bearings (TRBs). The sound sensing system was developed to replace the existing quality-control method conducted by human ears. All data collected by proto-type were performed by using data processing module. The background was identified at a low frequency band. Peaks at 8 kHz were as reference check due to noises caused by a motor. Sound frequency spectrum of healthy bearing barely exhibited sharp impulses or peaks. The sound frequency spectrum of bearing with defects was prominent in the characteristic frequency, which was higher than the normal bearing.