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撞击自鸣噪声的控制(Ⅱ)——自鸣噪声能量与撞击力缓冲程度的关系

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

  • 摘要: 根据第一部分得到的撞击力所激发的振动能量表达式,本文进一步推导了自鸣噪声的能量公式。该式表明自鸣噪声的能量与被撞击物体的质量、形状、辐射效率、阻尼及撞击力的冲量、缓冲的程度和撞击点位置的关系,本文对采用缓冲方法来降低自鸣噪声进行了深入分析。计算了一些平板和梁受撞击时发生的自鸣噪声能量与撞击力持续时间τ的关系。冲量不变时,板类结构和梁类结构的自鸣噪声随τ的倍增,分别下降10dB和12dB左右。对一些板和梁进行了撞击试验,测量了撞击力随时间变化的波形及其频谱。同时亦测量了声场中某点的声暴露级SEL的相应变化,SEL的变化可代表自鸣噪声能量的相对变化,实验结果与理论计算比较符合。

     

    Abstract: 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.

     

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