Take me out to the ballgame: The acoustics of the softball bat piano

As a multimedia supplement for a recent article “Acoustics and Vibration of Baseball and Softball Bats” [Acoustics Today, 13(4), 35–42 (2017)] the author created a “softball bat piano” and played the tune “Take Me Out to the Ballgame.” The bat piano is a collection of softball bats, clamped at the handles, selected for their barrel frequencies. It is played by striking the bat barrels with a softball. The structural modes of the hollow cylindrical barrel of an aluminum or composite bat are responsible for the trampoline effect which affects the performance of the bat as it is used for the game of softball. However, the “hoop mode” which gives rise to the trampoline effect is also the source of the bat piano’s audible musical sound. The nature of these cylindrical shell vibrations will be discussed, highlighting similarities to the musical properties of bells and chimes. The influence of bat construction and materials on the “hoop frequency” will be explained, along with the process of selecting bats with a range of frequencies wide enough to form a musical scale. If time permits, video of additional musical selections will be shown.