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Exact geometrical data are difficult to measure on soundboards of historic instruments, because they are fixed on the instruments, and cannot be removed. In our project, the situation was specific for each type of piano. For the replica of N. Streicher 1800-05 made by Gert Hecher, accurate data were given by the maker. For the J.B. Streicher 1873, we were able to measure the geometry on a very similar instrument: a piano built by Paul McNulty, which is a copy of a piano made by J.B. Streicher for J. Brahms in 1868 (see figures below). For the three remaining instruments (N. Streicher 1819, J.B. Streicher 1836 and 1851), measurements were limited to the visible and accessible parts of the mounted soundboards.
Copy of the soundboard of the Brahms's piano (J.B. Streicher 1868) made by Paul McNulty.
Thickness profile measured on the soundboard made by Paul McNulty. The coordinates X and Y are in cm. Z (thickness) is in mm.
Another way to investigate the vibrational behavior of soundboards is to measured their eigenmodes. One method for this consists in measuring the frequency content of impulses generated with small impact hammers in different zones of the soundboard (see figures). All strings are damped during this procedure. High-resolution spectral analysis then allows to extract the most significant frequencies contained in these impulses. Such measurements yields interesting information on the spectral content of the soundboard vibrations in the different registers (bass, medium, treble) of the piano, which can be compared to the results of simulations for validation and model adjustment.
Example of impulse on a J.B. Streicher 1836 soundboard.
Peak extraction of the J.B. Streicher 1836 soundboard impulse.
JBS36_Sdb_Acc_6notes_V3.mp4Example of soundboard acceleration. Piano J.B. Streicher 1836 (Nr 2876). Accelerometer glued on the treble side. Played notes: B6 to F#6.
JBS51_Acc_Sdb_D#1_C2.mp4Examples of soundboard accelerations recorded in the bass side of the soundboard of a piano J.B. Streicher 1851, for the played notes D#1 and C2.
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