Summary: This learning object is in the form of a word problem with two separate parts. This question addresses the interfering patterns of two waves. This question is limited to only interference of 2-D sound waves, which is significantly different from the waves that are referred to as beats which are out of phase from one another, unlike interference which is in phase.

https://drive.google.com/file/d/0B0QC6s0d2sVlckFWdktkUS1BTXc/view?usp=sharing