For humans, hearing is limited to frequencies between about 20 Hz and 20,000 Hz (20 kHz), with the upper limit generally decreasing with age. Other species have a different range of hearing. For example, some dog breeds.................... http://en.wikipedia.org/wiki/Frequency作者: ilydy5800 时间: 3.6.2010 10:08
提示: 作者被禁止或删除 内容自动屏蔽作者: 穷二代 时间: 3.6.2010 11:54 本帖最后由 穷二代 于 3.6.2010 12:55 编辑