I feel like every time there’s a train in a movie, they show an engineer walking along the cars hitting each car’s undercarriage with a rod or hammer. I have also seen this in documentaries, so it’s not just Hollywood. What is the reason for this?
In: Other
As the other poster says, it’s ‘wheel tapping’. If there’s a crack, it breaks up the sound waves travelling around the wheel when it’s hit so it doesn’t ring with pure tone.
If you ever have a cracked plate or mug, the difference in sound can be quite noticeable when compared to another one in the set.
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