they can locate and steer clear of obstacles -- or locate flying insects on which they feed.

并能通过回声来确定并躲开障碍物，或找到它们赖以为生的昆虫。

and of offering to the tenants offices and apartments that please them.

和向租房人提供使他满意的办公室和住房。

Many people in industry and the Services, who have practical experience of noise,regard any investigation of this question as a waste of time;

在工业部门工作和在军队中服役的许多人对噪音有切身的体会，他们认为对这个问题进行调查是浪费时间，

As a shipbuilder, Cockerell was trying to find a solution to the problem of the wave resistance which wastes a good deal of a surface ship's power and limits its speed.

作为一个船舶技帅，科克雷尔在寻找解决波浪阻力的方法，因为波浪阻力浪费掉了船在水面行驶的大量动力，从而限制了船的速度。

and no father is confronted with his inability to 'buy'an education for his child.

也不存在父亲无力为孩子支付教育费用而犯难的问题。

a wave length (the horizontal distance between two wave crests),

波长（两个浪峰间的水平距离）