What Makes Sound Be Higher Or Lower?

Sound has a higher volume when the sound waves are more energetic, more forceful. Sound has a higher pitch when the sound waves are closer together in time or space.

Lower volume sound has less energetic sound waves; lower pitch sound has waves that are less frequent.

"What makes it that way" depends on the sound source. On my stereo, the volume is lower when I turn the volume knob counterclockwise. On my record player, the pitch is lower when I slow down the speed of the record.