I was checking through the questions on DSP Stack Exchange and found a question that I was also curious about. So i was following the question to see any solutions. An answer has been given by a well known DSP Stack Exchange member which I am unable to clearly understand. The person who has asked the question hasn't commented or asked any further clarification. He hasn't even upvoted it or marked it as correct. so can I go forward and add a comment saying can you please elaborate the answer to person who has answered the question in the comments section of his answer. The hesitation I have is that it is not my question he has answered to. So can I do that or not?
You can do a couple of things here...
Leave a comment asking for clarification. Be specific about what in the answer confuses you. The answerer might return to update it.
Post a new question, referencing the answer to the existing question and describing what you found confusing about it (again, be specific!)
Note that #2 has the advantage of allowing anyone to jump in and provide a clarifying answer - this is particularly useful when the answer may be perfectly understandable to someone knowledgeable in the field but somewhat opaque to those with less experience.
Note also that you can combine #1 and #2 by asking a new question and then offering a link to it in a comment on the original answer...