3 sentences

1. 我忽然听到了他的声音。

   wǒ hū​rán tīng​dào le tā de shēng​yīn.

   I suddenly heard his voice.

   Source: OpenSubtitles

2. 天忽然下起雨来。

   tiān hū​rán xià qǐ yǔ lái.

   Suddenly, it started to rain.

   Source: Dong Chinese Dictionary

3. 怪不得那天晚上你忽然不见了。

   guài​bu​de nà tiān wǎn​shang nǐ hū​rán bù xiàn le.

   No wonder you suddenly disappeared that night.

   Source: OpenSubtitles