Meet the Ball Picker from TrueBots: a robot that automatically collects balls and brings them to the base. It does not require human intervention to work. The robot picks up balls without pressing them into the ground. Once the ball tank is full, the Ball Picker goes back to its base to unload the balls, so they are washed.
The Ball Picker has a collection capacity of up to 18000 balls per day. It does not make a lot of noise either. More information is available here.