Piano Bridges

When you play the piano, what you hear is produced mainly by the soundboard, the very thin sheet of wood under the strings.

You know that all sound is a result of vibrations traveling through air.  And piano strings vibrate when struck by a hammer.  But even the biggest string can’t move enough air to be heard very far away.

To solve that problem (in pianos and all other acoustic, stringed instruments), a soundboard moves the air, instead. 

But how does the vibration get from the strings to the soundboard?  Bridges!

A bridge is a piece of wood that sits on the soundboard and transfers vibrations from the string to the soundboard.  A piano has two bridges on the soundboard:  a bass bridge and a treble bridge

In most stringed instruments, the strings are held against the bridge by pressure.  A piano, however, also uses tilted “bridge pins” to hold the strings firmly against the bridge so that all the vibration passes cleanly across to the soundboard.

The strings weave between the pins, which puts a great deal of pressure on the pins.  And the strings’ vibrations add to that pressure, especially in the bass, where the strings are so heavy and stiff.

When a piano is in a dry environment, the bridge pins can move because of all that pressure from the strings.  And if the pins move, the bridge can crack.

A cracked bridge can cause trouble in several ways:

·         poor tone from the loss of vibration transmitted to the soundboard

·         unwanted vibrations from the loosened pins 

·         tuning instability from strings which are not secured properly

Helping you get more from your piano, courtesy of the Central Iowa Chapter of the Piano Technicians Guild.  (© 2009)