Figure 10.

Conductance-based theory accurately estimates (RMSE ≈ 1%) Helmholtz resonance frequencies for various sound hole shapes. By contrast, resonance frequencies are incorrectly estimated from the circle-of-same-area approach. The conductance of the interacting sound holes of any instrument with multiple sound holes is determined from equation (2.3). The air-resonance frequency is taken to be the average of the half-power frequencies measured on either side of the air-resonance peak and is found to have insignificant variation of less than 1% across multiple measurements.