Page "Drum" Paragraph 14

The second biggest factor affecting the sound produced by a drum is the tension at which the drum head is held against the shell of the drum.

When the hoop is placed around the drum head and shell and tightened down with tension rods, the tension of the head can be adjusted.

When the tension is increased, the amplitude of the sound is reduced and the frequency is increased, making the pitch higher and the volume lower.