Use 'perceptible' to describe changes that are very small but still noticeable. There was a perceptible shift in the audience's mood.
Pro Tip 2/3
Emphasizing Difficulty
'Barely perceptible' means something is so slight that it's almost impossible to notice. The whisper was barely perceptible over the noise of the crowd.
Pro Tip 3/3
Physical Sensation
'Perceptible' often refers to things felt with senses, like a small sound or light touch. A perceptible breeze cooled the room.