Usually if you can't see where the energy went, it turned into heat.
The ball must warm up. Any air escaping in the next compression, would be warmed as would your hand.
And, yes acoustic energy is a form of kinetic energy.
A 100 watt sound system at running at full power, puts a watt or two of acoustic, energy into the air. It turns into heat when absorbed by the walls and furniture.
Big power amps have "damping". Negative feedback, from the output to the input of the amplifier. If the voice coil is in motion when it should stop, a voltage is generated by the voice coil's movement in the magnetic field of the speakers magnets. This voltage is amplified in the opposite phase and stops and reverses the motion. Accelerating and decelerating the cones motion is a lot of work, and accounts for most of the power used.
