1. The small stain on my shirt was barely noticeable, almost unnoticeable.
2. The changes in the painting were so subtle that they were almost unnoticeable at first.
3. The difference in sound quality between the two speakers was unnoticeable to the average listener.
4. His attempts to blend in with the crowd were so successful that he was practically unnoticeable.
5. The crack in the wall was so tiny that it was almost unnoticeable unless you looked closely.
6. The new paint color on the walls was so similar to the old color that the change was unnoticeable.
7. The waiter moved so quietly and efficiently that his presence was almost unnoticeable.
8. The changes to the recipe were so minor that the taste difference was unnoticeable.
9. The missing button on her coat was unnoticeable until she reached to fasten it.
10. The typo in the document was unnoticeable to most readers, but it bothered the perfectionist editor.