ON THE CONTROL OF IMPACT RINGING NOISE （Ⅱ）——THE RELATION-SHIP BETWEEN THE ENERGY OF RINGING NOISE AND THE BUFFERING OF THE IMPACT FORCE

According to the expression of vibrational energy excited by impact obtained in the first of these two papers, the energy equation of ringing noise was derived in this paper. This equation indicates the relationship between the energy of ringing noise and the mass, the shape, the radiation efficiency, the damp of the impact bodies, the impulse, the buffering of the impact force and the position of the impact point. The buffering method used to decrease the ringing noise was discussed here in detail. The ringing noise of some plates and beams as a function of the duration of the impact was calculated. For a constant impulse, the energy of the ringing noise of the plate-like and beam-like structural parts decreases by about 10 dB and 12 dB respectively when the duration τ doubled. The wave form and the spectrum of impact force as well as the variation in sound exposure level （SEL） at a fixed point were measured which representing the relative changes of the ringing noise. The results of experiment agree with the results of calculation fairly well.