SOLUTION: 

I decided to create a simple pot plant that on the surface would just look like a normal piece of home decoration, so that it does not embarrass the users when there are guests over at the house. What this little plant does is that whenever someone places their cutlery down too loudly, clashes plates together, shouts at each other on the dinner table, its two leaves will drop off the stalk, expressing its sadness. I chose this movement since it was subtle enough to not be a nuisance to the user and also so it does not interrupt the overall dining atmosphere, but would be noticeable enough so that the user is aware that they have done something wrong.