Question

Empty vessel sounds much

Answer 1

Empty vessels make more sound That’s because the air column (i.e. the empty space) allows sound waves to pass through and bounce off the sides of the glass, which creates an amplified vibration

Answer 2

Empty vessels make much sound is the common and old proverb.

It means that people with no knowledge will make a huge fuss and the people with all knowledge are usually calm minded.

The emptiness can be in heart, mind, spirit or life. Hence, it is important to be calm so that you don't show anyone that you are empty.