Transparency mode (also called ambient mode, hear-through, or aware mode) uses the same external microphones used for ANC to capture ambient sound and play it through the headphone drivers. The result: you hear your surroundings as if you were not wearing headphones at all — announcements, conversations, traffic, doorbells.
The quality of transparency mode varies significantly. Apple's AirPods Pro 2 and Max have the most natural-sounding transparency mode — voices sound clear and present, not tinny or processed. Sony and Bose are close behind. Budget ANC headphones often have a noticeably processed, compressed-sounding transparency mode that works for alerts but feels unnatural for conversation.
Adaptive transparency (found on AirPods Pro 2) automatically reduces sudden loud noises like sirens or construction while keeping voices clear — a safety feature for urban use.