voice
咾 centers on the human voice as a sound produced by the mouth. It is a rare character whose given meaning is simply "voice."
咾 combines 口 (mouth) with 老, which likely contributes the sound. The exact historical development is uncertain, but the structure suggests a phono-semantic compound related to voice.
The mouth 口 beside an old person 老: imagine an old person's voice coming from their mouth, clear and distinct.
For ロウ, picture an old person's low voice rumbling from their mouth: low -> ロウ, and the sound fills the air.
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