A series of measurements is taken on two concert grand pianos in seven different stages of production, starting with the glue-laminated soundboard planks and ending with the completely assembled piano in concert tuned state. Due to the large size of the soundboard as well as its irregular shape, measuring deflection shapes is a nontrivial task. Common measurement tools such as piezoelectric accelerometers can affect the acoustic vibrations of the soundboard due to the added mass. To this end, a noninvasive microphone array method is utilized for the present work. The array consists of 105 microphones successively placed parallel to the soundboard, resulting in a total number of 1289 microphones covering the entire surface. The Soundboard is excited using an acoustic vibrator at 15 positions associated with string termination points on the bass and main bridge. Impulse responses are obtained using the SineSweep technique. The measured sound pressure can be back-propagated to the radiating soundboard surface using a minimum energy method. Based on the measured vibrational and acoustical data a set of signal features is derived which cover direct physical behavior (e.g., driving point mobility, damping, radiation efficiency) as well as perceptive parameters (e.g. attack time, spectral centroid). The empirical findings will contribute to a software tool (based on a real time physical model) to help piano makers estimate the impact of design changes on the generated sound.

Composite materials facilitate the control of specific properties in components while varying the type, angle, and order of individual fiber weaves in the laminate. This possibility of synthesizing material properties has aroused great interest in musical instrument making since the availability of synthetic fiber composites in the 1970s. However, when arranging plies, the combination of weave types and angles can lead to vibroacoustic effects which are unusual for makers used to working with wood. The mechanics behind these effects are described, starting with an outline of the theory of vibrations in thin plates. Further, the consequences of rotating fibers are theoretically derived and, subsequently, examined in a series of measurements on rectangular thin plates as well as assembled violin top plates. From the findings obtained, it can be concluded that the specific characteristics have to be taken into account for a successful use of composite materials in musical instrument making. This paper, therefore, concludes with easy-to-understand recommendations for musical instrument makers when using fiber composites.

Microphone array measurements of a grand piano soundboard show similarities and differences between eigenmodes and forced oscillation patterns when playing notes on the instrument. During transients the driving point of the string shows enhanced energy radiation, still not as prominent as with the harpsichord. Lower frequencies are radiated stronger on the larger side of the soundboard wing shape, while higher frequencies are radiated stronger on the smaller side. A separate region at the larger part of the wing shape, caused by geometrical boundary conditions has a distinctly separate radiation behavior. High-speed camera recordings of the strings show energy transfer between strings of the same note. In physical models including hammer, strings, bridge, and soundboard the hammer movement is crucially necessary to produce a typical piano sound. Different bridge designs and bridge models are compared enhancing inharmonic sound components due to longitudinal-transversal coupling of the strings at the bridge.

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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 constant of the model is varied according to a range similar to those found with measurements on a real grand piano at different production stages. With strong damping, a clear driving-point dependency of the forced string oscillation on the oscillation pattern of the soundboard is found. When decreasing the damping, this driving-point dependency is decreasing, nevertheless, it is still present. High damping, therefore, decreases soundboard vibration when strings drive the soundboard at the soundboard’s eigenfrequencies. However, such large damping increases soundboard vibrations when strings drive the soundboard at frequencies which are not eigenfrequencies. Therefore, strong damping smooths out the frequency response spectrum of an instrument. Extreme damping without any presence of distinct eigenmodes leads to a radiation of the strings sound spectrum 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 process by choice of materials, including wood or varnish, and geometry. Additionally, damping reduces the presence of ’dead spots’, notes which are considerably lower in volume compared to other notes.