If listen carefully and learn to imitate that sound, you can use the sound to get the babies attention. If I have a doe with a lot of babies and would like to have her feed them a little extra, I just go to the cage make the sound and the babies all start wiggling and squeaking. The doe will usually give me a dirty look, stomp at me, then go in the box and feed the babies to settle them down. All the babies respond to the sound until they are about four weeks old. After the first four weeks the response slowly diminishes.
Rabbits use a lot of body language in conjunction with the sounds.
They will leap and jump for joy. Circle your feet to welcome you home or get your attention. Sometimes they will touch your ankle with their nose to let you know they are there waiting for some pets. They learn very quickly to sit up and beg for what they want. There are also the signs that communicate their state of health.