Cascading open tone holes act as a frequency-based filter shaping woodwind timbre

Evidence

The presence of a sequence of open tone holes in a pipe resonator of any shape is described by Benade (1976) as a tone-hole lattice. The effec­ tive acoustical end-point of the pipe varies slightly as a function of fre­ quency when there is a tone-hole lattice, and therefore the effective pipe length is somewhat different for each mode. A pipe with a tone-hole lattice is acoustically shorter for low-frequency standing wave modes compared with higher-frequency modes, and therefore the higher-frequency modes are increasingly lowered slightly in frequency (lengthening the wavelength low­ ers the frequency). Above a particular frequency, described by Benade (1976) as the open-holes lattice cut-off frequency (given as around 350–500 Hz for quality bassoons, 1500 Hz for quality clarinets and between 1100 and 1500 Hz for quality oboes), sound waves are not reflected due to the presence of the lattice. Benade notes that this has a direct effect on the perceived timbre of woodwind instruments, correlating well with descrip­ tions such as bright or dark given to instruments by players. — David Howard, Jamie Angus, coustics and Psychoacoustics, 1246

Categorization

• DEFINE: Introduces ‘tone-hole lattice’ and ‘open-holes lattice cut-off frequency’ as technical concepts connecting pipe geometry to timbre.
• XREF: Connects physical pipe acoustics to the perceptual bright/dark timbre vocabulary — a classic psychoacoustics bridge between physics and perception.