Which makes the higher sound a trombone or trumpet and why?

A trumpet produces a higher sound than a trombone. This is because the length of the instrument affects the pitch of the sound. The longer the instrument, the lower the pitch. The trumpet is shorter than the trombone, so it produces a higher sound.

In addition, the mouthpiece of a trumpet is smaller than the mouthpiece of a trombone. This also contributes to the higher pitch of the trumpet. The smaller the mouthpiece, the higher the pitch.