When he heard a voice thus calling to him, he was standing at the door of his box.
calling to him可以理解为宾补吗,听到一个声音在呼唤他?还是定语,听到呼唤他的一个声音?
When he heard a voice thus calling to him, he was standing at the door of his box.
calling to him为目前分词作宾补。结构为“hear +名词/代词+doing sth=听见...正在做某事”