What is the meaning of 隔音符號?

apostrophe used to divide syllables within a word to avoid ambiguity in various alphabetic systems used in China; in pinyin, to be used between two syllables in a word (unless a hyphen is being used) whenever the second syllable begins with an a, o or e (regardless of whether any ambiguity exists) and not in any other circumstance

Source: wiktionary.org