I've posted a few threads on beat frequency, but I still need help. I know that it's really simple, and once I get it I'm gonna kick myself for being so stupid, but it just won't get through my head. I made a chart to help me figure out which possibility is the original one in beat frequency problems. I was only able to complete half of it. A sample problem is: When a guitar string is sounded against a 440 Hz tuning fork, twelve beats are heard in two seconds. a) What are the possible frequencies of the string? b) If the person tightens the string, the beat frequency decreases. What then is the original frequency of the string, and why?