Trained ears

Recently my car suddenly threw up an ‘Engine Fault’ warning and I called my mechanic, who said to bring it straight over. When I arrived I pulled up, got out, and started to describe the situation. Before I could finish he said, ‘I can hear it’s only running on three cylinders’. What sounded like a small engine growling and a fan going into overdrive was much more nuanced to him. It reminded me of when I traveled across Russia by train many years ago. Often when we got out at a station while the train stopped at the various towns and cities along the way there would be attendants walking down the train hitting the undercarriage - the mechanics and wheels - with big, heavy wrenches. The metal on metal of the strikes produced tuned percussive tones, which chimed down the platform. The workers were seemingly listening for anything out of place. Trained ears.