"突然厉声说出" can be translated into English as "suddenly blurt out in a harsh tone" or "abruptly speak out sharply".
Here are some example sentences to illustrate the usage:
1、 He suddenly blurted out in a harsh tone, "Stop that right now!"
(他突然厉声说出:“立刻停下!”)
2、 She abruptly spoke out sharply, demanding an immediate explanation.
(她突然厉声说出,要求立即给出解释。)