2 girls are listening to a program. Both are the same distance from the speaker which is 10 cm in diameter and enclosed in a box, but one girl is in front of the speaker while the other girl is to one side. What is the difference in the sounds reaching the two girls? does this affect, clarity of speech? Would removing the speaker from the box change anything?
I am presuming that the sound is coming only out of the speaker & both the girls are in the far field. If this is the case, then you have a standard baffled piston problem.
In that case, the sound emanating is highly directional when ka>>1. So the girl directly in front of the speaker will hear all the frequencies as intended. But the girl at an angle will not receive the higher frequencies at the same amplitude. So she will perceive the sound as if it is going through a low pass filter. You can see a demo of the amplitude distribution of a speaker in this site at the very bottom