Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you: You need to be quiet. She's (しず) being nice and quiet, unlike you!
We'd prefer a house on a quiet street.
I know you have diarrhea, but could you keep it down a bit more, please?
When Koichi and Viet got in, the taxi quietly started to move.