人耳可闻的某一振动频率可听声的声强范围。不同频率的可听声的声强范围不相同，频率约为2000Hz～4000Hz时，可听声的声强范围最大，即听觉灵敏度最大。当频率增大或减小，灵敏度就逐渐降低。频率小于20Hz或大于20000Hz时，无论声强如何都不能引起人耳对声音的感觉。
其它症候变化较多，例如足部下凹、脊柱侧凸、听觉灵敏度的减退或者糖尿病的出现。
Other signs are inconstant, such as the presence of hollow feet, scoliosis , decrease of the auditive acuteness or diabetes.
另一个在耳机上比较明显的听觉现象是长时间聆听造成的听觉灵敏度下降。因为耳朵会适应大音量的声音；
Another hearing phenomenon that seems to be more noticeable with headphones is a decreasing sensitivity to sound levels over time, as the ears adapt to loud sounds.
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