maintain loudness and tuning.
- Toneholes change the effective length of an air column.
- The larger the hole, the more the effective length is changed.
- The effective length of a bore with open tone holes is found to vary with frequency. The air column ``acts'' longer at high frequencies than at low frequencies.
- A tonehole lattice acts as a filter which transmits high-frequency sound components but reflects low-frequency components.
- The cutoff frequency of the tonehole lattice is an important factor in determining the timbre of the instrument.