Answer:
Depends
Explanation:
This depends on the amount of work the energy requires
The girl will hear an ECHO of the sounds that reach her,
(if she is standing more than about 50 feet from the wall).
In order to change from 45 m/s up to 9 m/s down, the velocity
of the ball has to change by (45+9)= 54 m/s downward.
Gravity adds 9.8 m/s of downward speed to any falling object
every second.
So the change takes (54/9.8) = 5.5 seconds .