Use of the hammered dulcimer to demonstrate physical acoustics principles

Abstract

In 1636 AD, Marin Mersenne described the law of vibrating strings that relates frequency to length, tension, and density in L'Harmonie Universelle. One of the instruments described by Mersenne is the psalterion or hammered dulcimer. The dulcimer is a versatile struck-string instrument, based on the circle of fifths, in which the sound generation and radiation are linked to many physical acoustics principles. Some of these principles are basic: how string properties affect fundamental frequency; how the soundboard and body cavity give rise to different resonances; how hammer construction and excitation affect the spectrum; etc. Because of the ease of demonstrating acoustical principles with the hammered dulcimer, a 9/8 backpack-size dulcimer has been included as part of the new ASA outreach workshops held in conjunction with semiannual meetings. A description of these efforts and a short demonstration of the hammered dulcimer will be given. More advanced concepts to be discussed include high-speed video results of the hammer-string interaction as well as near-field acoustical holography analyses on a 16/15 Songbird® dulcimer. The holography shows how the sound holes, traditionally thought to be merely decorative, significantly influence the radiated sound.