Answer: The suffix in "voiceless" is "-less".
Explanation: A suffix is a morpheme that is added at the end of a word in order to form a new word. When a suffix is affixed to an already existing word, the word category may change. The suffix in the word "voiceless" is "-less", which means "without something". In that way, "-less" has been affixed to "voice", which is a noun, and this has led to a change of the word category since "voiceless" is an adjective.