Characterizing Classical Guitars Using Top Plate Radiation Patterns Measured by a Microphone Array

Three guitars are measured using a microphone array and reconstructing their radiation patterns. All tones up to the 12th fret of the soundboard are played and analyzed for 20 partials each and back-propagated to obtain the radiation patterns. Four parameters were calculated from these radiation patterns, the radiating area, impedance, pressure reconstruction 1 meter in front of guitar top plate and Interaural Cross Correlation (IACC) as a binaural parameter. The guitars used showed distinct timbre differences, the Wichmann bass-reflex guitar has increased overall loudness with decreased tone variability, the Hanika concert guitar shows a very stable tone throughout playing range, and the low-priced Yamaha flamenco guitar has an rather unstable, semiprofessional tone. The calculated parameters were associated with these guitar characters, explaining the strong radiation and small variation of the bass-reflex guitar by decreased radiation area, associating the more stable sound of the Hanika guitar to a stable IACC behaviour, and the more unstable timbre of the Flamenco guitar to a strong variability over the different parameters used. When correlating the parameters for all guitars it appears that the correlation is independent of the guitar used and so appear to be a constant in guitar acoustics.