1 Corinthians 14:8 asks: if which instrument gives an unclear call, who will prepare for battle?

Answer: The trumpet

"If the trumpet sounds a muffled call (KJV: an uncertain sound), who will prepare for battle?" Paul uses it to urge clear speech.

“Again, if the trumpet sounds a muffled call, who will prepare for battle?”— 1 Corinthians 14:8 (BSB)