Sound Waves and Destructive Interference question

[BrooklynBees]

The problem:
Two speakers emit a sound with a frequency of 550.0Hz. At what distance should they be placed to maximize destructive interference?


I have the steps in solving this problem written on my worksheet, and it says that the speakers should be placed at 1/2 wavelength. The thing I don't understand is WHY they should be placed there. Other than that, I understand how to finish solving the problem. I just don't understand what the deal is with 1/2 wavelength.

Thank you!

 

[G01]

You want the sound waves (assumed to be in phase) to destructively interfere? What does this mean in terms of two waves overlapping? i.e. What part of wave 2 must overlap with a crest on wave 1 to cause destructive interference?

You should see (if you draw the waves coming from each speaker to scale) that this overlap will happen if the two speakers are half a wavelength apart.