Measuring the driving-point impedance of a stringed instrument's body is key in
obtaining its acoustic characteristics [30,31].
To obtain the driving-point impedance of the guitar body, an impedance head
accelerometer is placed in contact with the guitar on or close to the bridge.
This sensor outputs the accleration at its point of contact.
Accelerometers are typically very low load bearing thereby obtaining accurate measurements
up to very high frequencies.
As defined in Section 2.3.1,
the velocity and force are used in computing the driving-point-impedance. In the following subsection,
we present two methods for exciting the motion of the guitar bridge. With each method,
the force signal is measured and used in conjunction with the acceleration measured
to compute the driving-point impedance of the bridge.