Tā mófǎng lǎoshī de yǔqì wéimiào-wéixiào, quánbān dōu xiào le.
He imitated the teacher's tone so perfectly that the whole class laughed.
Tips
usage
肖 here is read xiào ('to resemble'), not xiāo. The idiom applies to imitations - paintings, impressions, descriptions, performances - not to original creations. Praise for how exactly something matches its model.