对,Keep your voice down 有 声音小点的意思
但是,反义句不可以说 keep your voice up
提高声音的正确英语是 raise your voice
比如：can you raise your voice a little 你声音能提高一点吗?你能大声点吗?
也可以说 can you speak a little louder?
2.Keep your voice down 这里的down 是副词.
3.她喜欢躺着看书 / 她喜欢躺在沙发上看电视
She likes to read lying down
She likes to watch TV lying on the sofa
4.她喜欢坐在沙发上打电话
She likes to sit on the sofa when talking on the phone
或
She likes to sit on the sofa when making calls嗯，谢谢帮忙啦She likes to watch TV lying on the sofa， lying 这里是表示动作同事进行吗？谢谢She likes to sit on the sofa when talking on the phone 这个句子和上面类似，但是 这里的when不能没有是吗？谢谢She likes to watch TV lying on the sofa对， lying 这里是表示动作同事进行She likes to sit on the sofa when talking on the phonewhen 可以省略，但本人觉得 when 使句子更精确。