When it comes to synonyms for the phrase "not noticeably," there are a plethora of words and phrases that can be used. Some alternatives to this phrase include "barely perceptible," "hardly discernible," "not discernibly," "nonetheless small," "diminutive," "hardly noticeable," "inconspicuous," "subtle," "slightly," "minimally," and "faintly." These words and phrases convey the same meaning as "not noticeably" while also being more descriptive and precise. It's essential to have a variety of synonyms in one's vocabulary to spice up writing and avoid using the same phrases repeatedly, adding more color and depth to the language.