shout, be noisy
譟 centers on loud, disorderly vocal noise: shouting or being noisy, typically in a disruptive or clamorous way.
譟 combines 言 (speech) with 喿, which likely contributes the sound and the idea of noise or clamor. The exact historical development of 喿 is uncertain.
The left side 言 is speech, and the right side 喿 looks like a cluster of mouths (口) and trees (木) suggesting a chaotic, noisy scene. Picture many voices shouting among the trees.
For ソウ, imagine a noisy crowd shouting so loud it sounds like a saw: saw -> ソウ, and the noise is deafening.
motivating the troops on the battlefield with war drums and war cries