Thanks for asking this question. This gives me an opportunity to tell a bit of a story.
First of all, my answer: Yes, your robot can make all of the sounds it wants.
2 - Interpretation - Robot game text means exactly and only what it says, so take it literally whenever possible.
- Do not interpret text based on your assumption about intent, or on how a situation might be in "real life."
- If a detail isn’t mentioned, then it doesn’t matter.
- There are no hidden requirements or restrictions. If you’ve read everything, then you know everything.
There is no mention of sound from the robot anywhere in the rules, so "it does not matter".
Now the story. I was at a FIRST LEGO League tournament where at team from the Maryland School for the Blind was participating. The students were, for the most part, not completely blind, but had significant visual handicaps that it made it extremely difficult for the team to read the robot screen during the competion. They overcame this obstacle by programming the robot to give it sounds in various stages of the robot programming. When their team came up to the competition tables, we turned down the music and requested that the teams and audience keep the noise down for that match to enable the team to hear the robot. It was a great experience for both the team and those that saw them compete.
Best of luck for your team this season!