in a low voice 是副词短语， 表示“低声地,小声地”。
其中，in 是固定搭配，voice是可数名词，因此，需要加冠词a或变为复数形式，即in low voices。
例如：
1、Say it in a sing-song way, in a low voice, in a high voice, in a baby voice, or any other voice. 在这样的唱歌方式，在一个低声音，在一个高的声音，在一个婴孩的声音，或任何其他的声音。
2、 He said in a low voice, both his handson his back.
他低声地说，他的双手放在背后。
3、I Am a Photograph is the first of six sleazy, hard-to-find albums in which she flaunts a voice so heavy with lownotes it makes one wonder if she really isn't a man after all.
从她的照片上你都不会对任何一种年龄质疑，因为她总是充满活力，或者人工的斧凿，或者地驻颜有术地青春长留。
4、 She drew closer to me, then said something in a low voice that I could not understand.
她挨近我，低声向我说了些我听不懂的话。
5、 Then in a low voice he said to his dog.
然后用低沉的声音，他说他的狗。
扩展资料：
Speak in a low voice 意思是“低声悄语”
例如：
1、 Don`t speak in a low voice in class.
在课堂上不要小声的说话。
2、The mother told her son to speak in a low voice.
妈妈告诉她的儿子小点声。
3、You had better speak in a low voice in the library.
在图书馆里讲话最好声音低一些。
4、Speak softly; in a low voice.
温柔地说；声音很低。
5、Always speak in a low voice; try to be a soft-spoken person.
说话声音要低；做个说话声音温和的人。
英 [in ə ləu vɔis] 美 [ɪn e lo vɔɪs]
小声;低声地;悄声;窃窃本回答被网友采纳