Now once the ventricles have filled up, both of the atrioventricular valves snap shut, creating a long, loud sound that sounds a bit like " lub" .

现在一旦心室被血充满，所有的房室瓣都关上了，发出一个长、响的声音，有点像“lub" 。

That first heart sound, " lub" , is called S1, and the noise comes from the tricuspid and mitral valves snapping shut when the left and right ventricles contract, which happens at about the same time.

第一心音“lub”叫做S1，是在左、右心室同时收缩，三尖瓣和二尖瓣关闭时发出的声音。