Whisper in someone’s ear and watch them do the same
Have you ever noticed how people who are unable to speak loudly tend to murmur and receive a response in the same tone? If you haven’t, listen carefully next time. It is an instinctive reaction for humans to reduce their voices when they hear a whisper.
You can now utilize this method whenever you suspect someone is speaking loudly. Even if you murmur, “What is your favorite color?” and ask them, they will respond in a similarly quiet tone, “mine is red, yours?”