In Japan, there is a traditional custom to know the state of things by sound. Below are some examples.
◎Knowing the time when watermelon is ready to eat.
In the old Japanese summer, those who took up a watermelon ball and tapped it lightly to judge if it was ready to eat, often were seen. If the watermelon makes a pop sound when tapped, it means a proof and sign that it became ripe, juicy and sweet enough.

◎Inspecting the state of the content of can.
Hammering inspectors at can factories examine the state of the can’s content by tapping its lid with a thin stick and listening to the sound that comes back. They say that the experienced can know exactly the state of can’s contents by tapping it so that hammering sound can resonates in the 2.5 kilohertz range which the human ear is most sensitive to.

◎ Examination of tunnel walls.
The hammering examination of tunnels is a well-known means to find the concrete’s strange parts by hammering the walls inside and outside of the tunnel and by listening to the coming back sound. It is said that, by the difference in sound, the degree of lifting or peeling of the wall can be found and by the sound of hammering, even the looseness of the bolts that fix signboards and other equipments can be checked.
◎Knowing how fried food is well cooked.
It is said that professionals who make tempura and other deep-fried foods can feel the state of the ingredients put into the oil-pan by the subtle changes of the sound of oil. When the ingredients are well cooked, the popping sound of the oil changes, law or high, which is said to be very useful for grasping the finish of frying.
◎スイカの食べ頃を見分ける
昔の日本では夏になると、スイカの玉を手に取って表面をポンポンと軽く叩き、食べ頃かどうかを見分ける姿をよく見かけました。軽く叩いたとき、ボンボンと音が返ってくるものは果実が熟している証拠で、水分を多く蓄えて甘味も増しており、食べごろを迎えてわけです。

◎缶詰の中身の状態を調べる
缶詰工場にいる打検士は、缶詰の蓋を細い棒で軽く叩いて返ってきた音で、缶詰の水分が適量か、腐っていないかなど、中身の状態を調べます。ベテランになると、人間の耳がもっともよく感知できる2.5キロヘルツあたりの帯域で響くような叩き方をすることで、缶詰の中身の状態をより詳しく把握できるそうです。
◎トンネルの壁面を検査する
トンネルの打音検査では、トンネルの内部や外部の壁面をハンマーでたたき、響く音でコンクリートの異常個所を発見します。音の違いで壁面の浮き具合や剥離の程度などがわかるといい、看板などの機材を固定しているボルトの緩みも打音で確認するそうです。
◎揚げ物の火の通り具合を知る
天ぷらなど揚げ物をするプロは、油の中に投入した具材の状態を、音の微妙な変化で感じ取るといいます。具材に火が通ってくると、油のはじける音が小さくなったり高くなったりするため、揚げあがりの目安をつかむのに役立つということです。
NLP共同創始者ジョン・グリンダー博士認定校
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記事更新日:2023/06/26