moan, interjection for pain, sad
噢 centers on vocal expressions of distress: a moan, a cry of pain, or a sound of sadness. The interjection sense is a direct use of that pained vocalization.
噢 combines 口 (mouth) with 奧, which likely contributes the sound. The mouth radical points to a vocal sound, fitting the meanings of moaning or crying out.
The mouth 口 beside the complex 奧 shape suggests a deep, muffled sound coming from the mouth. Picture someone with their mouth open, letting out a low moan of pain or sadness.
For ユウ, imagine the drawn-out moan 'yuuuu' escaping from the mouth 口: the sound 'yuu' directly cues ユウ while the person moans in pain.