Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You haven't learned this reading yet, so here's a mnemonic to help you:
When you're in the library the librarian is always telling you to quiet down. She's (しず) so mean! She never lets you talk in the library. Who's mean to you? She's mean to you!!
For the time being, let’s wait until dad’s anger has calmed down.