不思議な音　釜鳴りの謎／A Strange Sound: The Mystery of “Kamanari”

DENJIRO: Today, I’d like to solve the mystery behind a strange sound. This can here contains boiling water. I’m going to put uncooked rice in here. Watch what happens. GIRL: What’s this sound? It’s so strange. DENJIRO: We can hear a very strange sound. This is a phenomenon known as “kamanari.” NARRATOR: Kamanari is a religious ritual held at Kibitsujinja shrine in Okayama Prefecture. A steamer and uncooked rice are used to read fortunes through sound. DENJIRO: So why is a sound produced? Let’s get to the bottom of this. I’ve changed the container to something made of glass so we can see what’s going on inside. The container is filled with steam. Now, let me add rice. The rice falls onto this platform here, and we hear a sound. The same thing happened with the can we saw earlier. Actually, what’s happening here is, the gas inside the pipe is vibrating. That’s why we hear a sound. To prove this, let me bring a sheet with sand on it over the pipe. The sheet vibrates along with the gas, and the sand moves around. Let me explain about the gas’s vibration using this spring here. Even before we hear a sound, the gas inside the pipe is slightly expanding and shrinking. It’s similar to how this spring is bouncing. NARRATOR: When rice is added, the gas is cooled by the rice. The gas shrinks from being cooled and expands from being heated by steam. This repetition amplifies the vibration. DENJIRO: The vibration of the gas inside the pipe is amplified, and a loud sound is produced. NARRATOR: This is known as “self-induced vibration.” This was the secret behind the mysterious sound. DENJIRO: I hope energy will bring you all happiness. Our magic word is "Happy Energy!"