Only during קריאת שמע

 

According to the מהרש"א &  צל"ח when the גמרא (Pesachim 56a) says, ברוך שם כבוד מלכותו לעולם ועד"  should be said quietly during the year except for יו"כ", it is only during קריאת שמע This is the reason why we do say* בשכמל"ו aloud  on יו"כ קטן (then we aren't likened to מלאכים ) *The original Minhag Ashkenaz was to say it only when a Minyan fasted.