lit. if you tap a half-empty bottle it makes a sound (idiom); fig. empty vessels make the most noise; one who has a little knowledge likes to show off, but one who is truly knowledgeable is modest
trad. 半瓶水響叮噹
Also written 半瓶水響叮噹【bàn píng shuǐ xiǎng dīng dāng】