to sob
唈 centers on the sound and act of sobbing: a choked, audible cry. The meaning is narrow and concrete, with no major distinct senses.
唈 combines 口 (mouth) with 邑, which likely contributes the sound. The character is used for the sound of sobbing, fitting the mouth radical.
The mouth radical 口 beside 邑 suggests a sound coming from the mouth. Picture a person with their mouth open, the shape of 邑 like a choked throat, producing a sob.
For オウ, imagine the sound of a sob: a low, drawn-out 'oh' that catches in the throat. The 'oh' sound cues オウ as the person sobs.