I am using an electroacoustic guitar. Anytime I start to play, either picking or strumming it gives me a weird sound. It sounds almost like the string keeps vibrating and seem to be hitting the frets. I have changed the strings because I suspected it was as a result of old strings but it keeps giving me the same problem.
It's hard to tell for sure without looking at your guitar but it sounds like the strings are too close to the frets at some point on your guitar.
When you pluck a string on a guitar, it vibrates in an oscillating manner. That means it vibrates up and down as well as side to side - sort of in a circle. If any of your strings are too close to any of the frets, they can come in contact with the frets when vibrating. If this is what is happening, you will notice more fret buzz the harder you pluck the strings.
A fairly common happenstance that I see on many acoustic guitars is that there is a hump in the fretboard where the body joins the neck. Often that is where you get the strings hitting the frets.
If your guitar is tuned lower than standard or you are using lighter gauge strings than the nut slots are cut for, this could also contribute to fret buzz.
To correct this problem you might need to have a proper set up on the guitar. During a set up, the action (height of strings above the frets) will be adjusted by making adjustments to either the saddle (at the bridge) height - or the truss rod or both. In some cases, a high fret may need to be filed down with a fret file. A qualified guitar repair tech or luthier will be able to evaluate your guitar and make the needed adjustments.
You might be able to take this buzzing out by adjusting the truss rod which you can do yourself if you have the correct sized truss rod wrench. Ideally the neck will need to have a slight concave bow to give proper relief for the strings to oscillate without contacting the frets. If your neck is perfectly straight or back bowed when you sight down the fretboard - loosening the truss rod may help. You will want to make minor adjustments until your frets are no longer contacting the strings during normal playing.
Below is a link to a comprehensive step by step video explaining how to adjust your truss rod. Do not attempt to adjust your truss rod unless you have the exact correct size wrench. Stripping the truss rod can have serious and expensive consequences. Good luck.
without seeing or hearing the guitar, here are a couple of possibilities; (1) If it's your bass string(s) E / A that keep vibrating, then you may have the bass e.q. set to high (2) you may need set the action/intonation and neck adjustment (possibly fret leveling) to alleviate the fret buzz, no matter if it's only one string that seems to be causing the problem (3) The string(s) may be faulty/defect (not tightly wound enough) (4) There could be something loose on the guitar, that causes this vibration, such as part of the pick-up system or any of the screws, mountings-etc., that hold it in place. If you are not experienced in doing any of these repairs, then the best thing is to take it to your local luthier and have them look at it, to at least identify the exact problem.