Impact of damping on oscillation patterns on the plain piano soundboard

The influence of internal damping on the vibration of a piano soundboard is investigated using a Finite-Difference Time-Domain (FDTD) physical model and experimental measurements. The damping of the model is varied according to a range found with measurements on a real Grand D piano at different production stages. With strong damping, a clear driving-point dependency of the forced string oscillation on the oscillation pattern on the soundboard is found. When decreasing damping, this driving-point dependency is decreasing but still present. Large damping, therefore, decreases soundboard vibration when strings drive the soundboard at the soundboard’s eigenfrequencies. On the other hand, such large damping increases soundboard vibrations when strings drive at frequencies, not eigenfrequencies of the soundboard. Therefore strong damping smooths out the frequency response spectrum of an instrument. Extreme damping, i.e., no presence of eigenmodes, lead to a radiation of the strings sound without soundboard filtering. Low damping leads to a strong influence of the soundboard on the string’s radiated sound. Therefore the amount of soundboard characteristics can be designed to alter internal damping, e.g., by more or less varnish. Also, damping reduces the presence of 'dead spots', notes which are considerably lower in volume compared to other notes.