问题
名词解释
声阻抗
答案
参考答案：即声阻抗率或声特性阻抗，可以理解为声波在介质中传播所受到的阻力，等于介质的密度与超声在该介质中传播速度的乘积。设Z为声阻，ρ为密度，C为声速，则Z＝ρ·C。两介质声阻相差之大小决定其界面处之反射系数。两介质声阻相差愈小，则界面处反射愈少，透入第二介质愈多；反之，声阻相差愈大，则界面处反射愈强，透入第二介质愈少。
搜题请搜索小程序“爱下问搜题”
声阻抗
参考答案：即声阻抗率或声特性阻抗，可以理解为声波在介质中传播所受到的阻力，等于介质的密度与超声在该介质中传播速度的乘积。设Z为声阻，ρ为密度，C为声速，则Z＝ρ·C。两介质声阻相差之大小决定其界面处之反射系数。两介质声阻相差愈小，则界面处反射愈少，透入第二介质愈多；反之，声阻相差愈大，则界面处反射愈强，透入第二介质愈少。
It often seems that people have a hard time in speaking a seemingly familiar name. Did you ever have someone's name on the tip of your tongue and yet you were not able to recall it? When this happened，what did you do? Next time this happens again，what should you do? You should not try to recall it. Instead, just do something else for a couple of minutes and then the name may come into your head. Why? The name is just there, since you have met this person and learned his name. It, waiting there, only has to be dug out. The initial(最初的) effort to recall prepares the mind for operation, but it is the subconscious (下意识的) activities that go to work to dig up a dim（模糊的）memory. Forcing yourself to recall almost never helps because it doesn't loosen your memory; it only tightens it. That’s why students find the preparatory method greatly helpful in examinations. They read over the questions before trying to answer any of them. Then they answer first the ones of which they are most confident. At the same time, deeper mental activities in the subconscious mind are taking place; work is being done on the more difficult questions. By the time the easier questions are answered, answers to the more difficult ones will usually begin to come into consciousness. It is often just a question of waiting for recall to come to the memory. You see, forcing ourselves to think hard to recall something usually doesn’t help. Chances are that the harder we think, the more difficulty we face in thinking of what we want to. Offering our mind time to work is what we are expected to do.
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