James Cottingham: Sound Production in Free Reed Instruments - Experiments and Models
Western free reed instruments, including the reed organ, harmonium, harmonica and accordion, use asymmetric free reeds that are able to maintain sustained oscillation in the absence of a pipe resonator. Asian free-reed mouth organs, including the khaen, naw, bawu, sheng and sho, incorporate approximately symmetric free reeds coupled to pipe resonators. Previous research has shown that the reeds in the Asian instruments behave as “blown-open” reeds in which the sounding frequency is above both the natural frequency of the reed and the first peak of the measured impedance curve of the pipe, while the Western free reeds function as “blown closed” reeds, with sounding frequency is below the natural frequency of the reed. While free reed oscillation can be approximated as a sinusoidal oscillation of a cantilever beam in the fundamental transverse mode, it has been shown that higher transverse modes as well as the first torsional mode are present even at low amplitudes of oscillation, and are observable and possibly significant in the transient period before the oscillation reaches full amplitude. Efforts to model free reed sound production have included several theoretical models and as well as aerodynamic simulations.
Jim Cottingham is currently Professor of Physics Emeritus at Coe College. He has been working with undergraduate students in musical acoustics research 1990. During this time about 50 students have been involved, and the primary research emphasis has been on the acoustics of free reed instruments. He has become a recognized authority on the acoustics of free reed instruments, and has served as an invited speaker in this area at a number of national and international conferences. In 2011 he was the author of an invited feature article on free reed instruments in Physic Today. He was elected a Fellow of the Acoustical Society of America (ASA) in 2005 and has been active in the ASA in a variety of ways, including two three-year terms (1999-2005) as Chair of the ASA Technical Committee on Musical Acoustics. He also serves as a member of the Board of Advisors of the Interdisciplinary Center for the Study of Free Reed Instruments at the CUNY Graduate Center.