The bassoon tonehole lattice: Links between the open and closed holes and the radiated sound spectrum

The acoustics of the bassoon has been the subject of relatively few studies compared with other woodwind instruments. One reason for this may lie in its complicated resonator geometry, which includes irregularly spaced toneholes with chimney heights ranging from 3 to 31 mm. The current article evaluates the effect of the open and closed tonehole lattice (THL) on the acoustic response of the bassoon resonator. It is shown that this response can be divided into three distinct frequency bands that are determined by the open and closed THL: below 500 Hz, 500-2200 Hz, and above 2200 Hz. The first is caused by the stopband of the open THL, where the low frequency effective length of the instrument is determined by the location of the first open tonehole. The second is due to the passband of the open THL, such that the modes are proportional to the total length of the resonator. The third is due to the closed THL, where part of the acoustical power is trapped within the resonator. It is proposed that these three frequency bands impact the radiated spectrum by introducing a formant in the vicinity of 500 Hz and suppressing radiation above 2200 Hz for most first register fingerings.