Chinese · Pronunciation Guide
shya-WOO: a hard-falling first syllable with the thin x hiss, then a low sagging second that is a tightly rounded "oo".
xiàwǔ
Fall then dip, with no rule inside the word. But wǔ is a third tone at the right edge, and it converts readily: xiàwǔ yǒu and xiàwǔ hǎo both push it up to a rising tone. Time expressions like this one are very often followed by verbs, and 有 in particular is a dipping tone, so the conversion happens frequently.
Listen: 下午
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我下午有课。
Wǒ xiàwǔ yǒu kè.
I have class in the afternoon.
Listen: 我下午有课。
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我下午有课。 does exactly that. Wǔ and yǒu are adjacent third tones, so wǔ rises: xià wú yǒu kè. Wǒ at the start keeps its dip because xià falls. The sentence therefore drops, climbs, dips and drops again, and the conversion sits right in the middle where it is easy to miss.
Most learners substitute English "sh" for the x, which pulls xià toward the retroflex shà. Spread the lips and keep the tip down. On the second syllable, the rounding is often only halfway, giving something between "oo" and "uh". And the wǔ yǒu sandhi in the example crosses a word boundary, which is precisely the kind beginners overlook.