Cello Handbook/Buzzing

Apart from external causes of buzzing, such as a button on your clothes vibrating against the cello or even something in the room vibrating in sympathy as you play, buzzes can be caused by almost any part of the cello. Below is a list of the most common buzzes and possible causes.
Buzzing on only one string

There may be a loose string winding – if so replace the string.
A stopped string may buzz because of an oversized string groove at the

bridge; an open string buzz that disappears when the string is stopped suggests an oversized string groove at the nut
Buzzing only on certain notes

Your fingerboard may be uneven and the strings may catch on the bumps when you stop certain notes. If so, ask a luthier to smooth (‘true’ or ‘re-shoot’) the fingerboard for you.
Intermittent buzzing

Buzzes caused by loose purfling or open seams can disappear in damp weather and reappear in dryer weather as the glue softens and hardens. If in doubt, consult a luthier.
Other common causes of buzzing

The end of the tail-gut is buzzing against the tailpiece
Fingerboard is coming unglued
Loose adjuster – try tightening it down
Loose bridge vellums
Loose end pin (spike)
Loose end of a string buzzing inside the peg box
Loose decorations on pegs
Loose plastic sleeve bridge protector; either remove it or push it firmly down over the silk at the bottom of the string
Open (unglued or fresh) cracks
Poor contact between the bridge feet and cello front
Tail-gut vibrating in an over-sized hole in the tailpiece
Mute not placed correctly. If you are using a mute, ensure that it is secured.