There are many bits on an acoustic guitar that can rattle against each other to make a buzzing noise. Most can be easily fixed once you become aware of them but tracking that guitar buzz down can be a problem if you don't know where to look.

The first place to look for the cause of buzzing guitar is the guitar player. If you are not pressing down on the strings with the correct amount of pressure, the strings will buzz or sound muffled. This might not be entirely your fault if the guitar's action is too low. If the strings are too close to the frets you will get a buzz that no amount of pressure on the strings will fix.

To fix low action on an acoustic guitar is a matter of going to a guitar store and getting a bridge bone that will lift the strings higher. If the notches in the guitar nut are too deep this will also cause buzzing but that is the least likely cause unless someone deliberately cut the notches deeper. If the slots in the nut are too wide, this will also cause a buzz. A quick fix for low action is a match stick slipped under the bridge bone. If you find the guitar too hard to play now, it's because you have made the action too high.

If the guitar is old, you may have frets that are too worn. This will make the strings buzz against the higher frets. All the frets on the guitar need to be the same height.

If you are using strings that have balls on the ends, check that the balls are tight up against the bridge. If you find one that is not, unwind the string and reseat the ball so it is snug. The loose ends of nylon strings can also buzz against the bridge so if you have a classical style guitar, check the ends of the strings lying against the bridge.

The machine heads - the tuners at the top of the neck - can become loose with age, rattle around. It is probably best to not get involved in repairing them. Just buy a new set.

If you have checked all these parts without identifying the cause of the buzz, take your guitar to a luthier or a local guitar dealer to get it checked out. Sometimes there can be loose parts on an acoustic guitar that are not readily accessible that might need some guitar surgery to fix.