Notch filtering, an audio filtration technique, is proposed to reduce the vuvuzela sound in broadcasts and increase clarity of commentary audio. The vuvuzela produces notes at a frequency of approximately 235 Hz and its first partial at 465 Hz. However, this filtration technique affects the clarity of commentary audio. Proposals of adaptive filters by universities and research organisations address this issue by preserving the amplitude and clarity of the commentators' voices and crowd noise. Such filtration techniques have been adopted by some cable television providers.