does anybody know if a standing wave can be filtered to leave its original sinewave before reflection????
was thinking about using a bandpass filter but im not even sure if the idea will work....
help

 

I am not certain exactly what you mean, but there are directional couplers that kind of look like a 'T' the reflected wave is directed back out of a different port, leaving only the incident wave. Mini-circuits makes some of them.

 

Are you still talking about guitar waveforms? Standing waves indeed appear on guitar strings by virtue of reflections from the two ends. These are vibrations at a certain frequency, which depends on the length of the string, the type of string, the tension of the string, etc. The result is an acoustic (and electrical, if you have a pickup or microphone) sine wave at the vibration frequency.
I don't think you need to be concerned with standing waves if you are trying to process the signals from your pickups. Standing waves are mechanical. Their periods and amplitudes both have dimensions of length. They only show how the string vibrates, and how sound is being generated. The only thing you can process, or need to be concerned with, is the resulting electrical signal, which has dimensions of frequency (Hertz) and amplitude (volts).