target, splashboard on chariot
靶 centers on a target or mark to aim at, originally a splashboard on a chariot that served as a visible aiming point. The two given meanings connect through the idea of a designated object to hit or strike.
靶 combines 革 (leather) with 巴, which likely contributes the sound. The original meaning referred to a leather splashboard on a chariot, later extended to a target for archery or striking.
Leather (革) is stretched over a frame shaped like 巴, forming a target. Imagine an archer aiming at a leather-covered target marked with a spiral 巴 pattern.
For ハ, picture a target with a big 'ha!' sound as the arrow hits: ha -> ハ, and the leather target absorbs the impact.