A simple experiment quantifies the difference between the sound production of
a banjo with and without a resonator back. Driven by a small tweeter mounted
inside the pot, for frequencies above about 4500 Hz, the produced external
sound is 6 to 10 dB louder with the resonator than without. With the banjo
played in any normal fashion, this gives a negligible contribution to the
overall volume. However, that difference is clearly a reflection of the
universally recognized resonator sound, in close analogy to plosive consonants
in human speech. No direct correlation is observed between the head-resonator
separation and the spectrum of the enhanced response. This suggests that direct
reflection off the back is not a primary contributor to the resonator/openback
difference, leaving differences in overall absorption as the major suspect.Comment: 19 pages, 6 figures, 4 mp3 file
