本帖最后由 穷二代 于 3.6.2010 08:15 编辑
哈哈笑死我了~~~~
可以听到超过20的童鞋们,你们可以去申请改全世界的教科书了
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 |