Focus on the pronunciation of imperceptible
English definition of “imperceptible”
/ˌɪm·pərˈsep·tə·bəl/ adj [not gradable]
› (of an action or change) so slight that it cannot be noticed: When they brought her in to the emergency room, her breathing was imperceptible. imperceptibly
/ˌɪm·pərˈsep·tə·bli/ adv › Imperceptibly, the day grew darker.