Audio Engineering Society

Chicago Section

Meeting Review, September 27, 2005


other meeting reports

9/27/05 Meeting Highlights
by Jeff Segota

On September 27th, the Chicago Section gathered at Columbia College in Chicago for the

presentation The Acoustics and Vibrations of the Concert Harp including New Design

Developments with Composite Materials. Author Melinda Carney studied the harp and

composite materials for her master’s thesis, and is currently a faculty member at Columbia and a

PhD candidate at University of Illinois, Chicago. About thirty-five attendees were treated to a

rigorous analysis of harp physics as well as a live demonstration and recording session with a

classically trained harpist.

 

 

The presentation started with an analysis of the harp as we know it today, including a brief

history, wood selection, soundboard construction, and soundboard and string vibration and

radiation. Since wood is susceptible to cracking and changes with humidity and is in short

supply, research into alternative soundboard materials has been ongoing. The author described

her recent research, starting with modal and finite element analysis to determine the wood’s

material properties and determine matching criteria for experimental materials. Carbon fiber

composite materials were covered next, particularly the relationship between the number and

orientation of plies and the resulting mechanical properties. Experimental soundboards were

constructed, and the initial results showed that it is possible to get the resonance frequencies of

either the bending modes or the torsional modes to match, but not both. This observation led to

an additional criterion, more experimentation, and better results, however, the damping of the

composite soundboard was only half that of wood. The author showed the finite element

analysis results for the wood and composite boards, and finished with recommendations for

further research including a full composite soundboard.

 

The meeting concluded with a lively discussion period, followed by the live demonstration in the

college’s recording studio.