Just then he heard the big drum say, Come, come! Come, come!

就在这时，它听到大鼓响了起来，来啊，快来！来啊，快来！

I upgraded... got a bigger drum, got a bigger motor — and I was in business.

我升级装备，买了一个更大的滚筒，买了一个更大的电机——我开始了业务。

It's a big drum with a spinning rotor that contains magnetic poles, which creates a really strong, magnetic field called an " induction field" .

它是一个有磁性的飞速旋转的大滚筒，一个可以创造出“感应场”的强大磁场。

When it was time for troops to attack, a commander told his musicians to beat big drums.

当军队进攻的时候， 一位指挥官命令他的乐手敲响大鼓。