noisy
譁 centers on loud, clamorous noise, especially from voices or a crowd. The single given meaning 'noisy' captures this idea directly.
譁 combines 言 (speech) with 華, which likely contributes the sound and may suggest a flourishing or extravagant quality, together giving the idea of loud, flourishing noise.
Words (言) that are as showy and over-the-top as flowers (華) create a noisy, clamorous scene.
For カ, imagine a noisy car (カ) honking while people shout over each other: car -> カ, and the noise is overwhelming.