soundpost

noun

music a small post, usually of pine, on guitars, violins, etc, that joins the front surface to the back, helps to support the bridge, and allows the whole body of the instrument to vibrate

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Examples from the Web for soundpost

Historical Examples of soundpost

The soundpost must engage your closest attention, and must be of old Swiss pine.
Violin Making
Walter H. Mayson