Our work on the physics of the piano soundboard is just beginning, but we have already produced some very interesting results. We are primarily concerned with understanding the motion of the soundboard and all of the parameters that affect it.
Using our electronic speckle pattern interferometer we can visualize the deflection shape of any frequency of vibration. The pictures below show time-averaged electronic speckle pattern interferograms of the back of a completely assembled spinet piano as it is driven at three different frequencies. Each black ring represents approximately 250 nanometers of displacement. To our knowledge these are the first interferometric studies of a piano soundboard in situ.
We have recently built a computer model of this particular soundboard to investigate the importance of each part. Comparing the interferograms with the results from this model have lent considerable insight into why soundboards move as they do. An article reporting this work has been accepted for publication in The Journal of the Acoustical Society of America, and is scheduled for publication in the March 2006 journal.
We are also studying the soundboard of a fully assembled grand piano. This work is centered on understanding the importance of the string tension on the soundboard resonances. Below are some interferograms of the soundboard of a grand piano as it vibrates.
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