In general, the the string or air column of a musical instrument is, the more harmonics are generated.

In general, the LONGER the string or air column of a musical instrument is, the more harmonics are generated.

close lines strong magnet less close weaker

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me